Low latency wireless protocol

ABSTRACT

This application relates to electronic devices configured to connect to a wireless local area network and communicate using a trigger-based access mechanism. An access point is configured to define a contention-free period associated with a communications medium utilized by the wireless local area network. During the contention-free period, the access point allocates transmission opportunities to each of a number of electronic devices by transmitting trigger frames to the electronic devices via the communications medium. Each trigger frame can be directed to a particular electronic device and indicates to that electronic device that the current transmission opportunity has been allocated to that electronic device to transmit data (e.g., frames) to the access point via the communications medium. The access point implements an algorithm for allocating two or more transmission opportunities within a contention-free period to two or more corresponding electronic devices.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Application No.62/738,668, entitled “LOW LATENCY WIRELESS PROTOCOL,” filed Sep. 28,2018, the content of which is incorporated by reference herein in itsentirety for all purposes.

FIELD

The described embodiments relate, generally, to wireless communicationsamong stations in a wireless local area network (WLAN), includingwireless (electronic) devices and access points, and techniques forproviding low latency wireless communications in a real-timeenvironment.

BACKGROUND

Many wireless local area networks (WLANs), such as those based on acommunication protocol that is compatible with a set of Institute ofElectrical and Electronics Engineers (IEEE) 802.11 standards, alsoreferred to as ‘Wi-Fi’, involve contention-based, distributed accesssystems. Typically, the WLANs are contention-based because they utilizeunlicensed radio frequency (RF) bands or spectra, which areunpredictable and are often subject to interference. Theunpredictability of the interference can make coordination acrossmultiple electronic devices, also referred to as stations (STAs),challenging (especially for an unmanaged WLAN), and can result infailure of a contention-free period (CFP).

Legacy Wi-Fi can rely on contention-based, multi-user transmission inthe uplink referred to as Carrier Sense Multiple Access, CollisionAvoidance (CSMA/CA). Each station (STA) listens to one or morecommunication channels to determine whether the communications medium isbusy. If the communications medium is idle, then a STA can attempt totransmit data to another STA during a time period that is divided into anumber of backoff slots. Each STA selects a random backoff slot within acontention window, e.g., using a backoff timer, and can transmit duringthe selected backoff slot if the communications medium remains idleuntil expiration of the backoff timer. If another STA transmits on thecommunications medium before the backoff timer has expired, then the STAresets the backoff timer and waits until the next frame to re-attempttransmission over the communications medium. However, if the backofftimer expires before another STA attempts to transmit over thecommunications medium, the STA will attempt transmission over thecommunications medium. However, attempting the transmission does notensure that another STA has not randomly selected the same backoff slotto attempt to transmit over the communications medium, thereby causing acollision to occur when both STAs attempt to transmit during the samebackoff slot. Failure of the STA to receive an acknowledgment framecould indicate that a collision occurred, and the STA can attempt toretry transmission after doubling the size of the contention window todecrease the probability of another collision during the nexttransmission opportunity.

The contention-based access mechanism for legacy Wi-Fi, described above,leads to unbounded latency for transmission of data packets, where theexpected latency is correlated with the number of STAs transmitting overthe communications medium. Large number of STAs attempting to transmiton the same communication channel can result in a high probability ofcollisions, which can quickly lead to latencies in the hundreds ofmilliseconds (ms). While these latencies are tolerable for someapplications, such as requesting a web page on a wireless device,latencies of hundreds of milliseconds are intolerable for real-timeapplications such as audio streaming, virtual reality, and gaming.

Contention-free, multi-user transmission in an uplink direction from aSTA to an access point (AP) has been proposed for inclusion in the IEEE802.11ax standard. This approach can dramatically change how a wirelessdevice accesses the communications medium. In particular, a wirelessdevice can transmit without contending for the communications medium.Instead, a primary STA (e.g., the AP) controls access to thecommunications medium for the STAs connected to the WLAN by grantingtransmission opportunities to each individual STA using a trigger frame(which may be referred to as ‘trigger-based access’ or ‘trigger-basedchannel access,’ for uplink multi-user transmission). In principle, theuse of trigger-based access and multi-user transmission cansignificantly reduce contention for access to the communications mediumby the wireless devices in the WLAN. Consequently, trigger-based accessis expected to result in improved communication performance. However,this contention-free access mechanism does little to alleviatecontention issues with multiple WLANs attempting to communicate over thesame communications medium (e.g., where multiple access points in closeproximity implement different WLANs on the same channels of thecommunications medium).

Furthermore, trigger-based access and multi-user transmission cansignificantly increase energy consumption of the wireless devices in theWLAN. In particular, for N wireless devices sharing a communicationchannel, the average data bandwidth can be reduced by a factor of N and,therefore, the energy required to transmit the data can be increased bya factor of N. Moreover, the access overhead in the WLAN typicallyincreases with trigger-based access and multi-user transmission.Furthermore, this approach for allocating shared resources can beinefficient (including wasted or unused resource units and, moregenerally, suboptimal channel utilization) and inflexible (because thewireless devices can be required to transmit over the same duration timeperiod using identical data rates). In addition, trigger-based accessand multi-user transmission is not backwards compatible with existing orlegacy wireless devices.

SUMMARY

Some embodiments regard an access point that controls access to acommunications medium for a set of electronic devices connected to aWLAN. In particular, during operation, an interface circuit in theaccess point transmits a trigger frame that includes informationspecifying an ordered list of electronic devices that are allowed totransmit data via a communications medium during a contention-freeperiod. Subsequently, the interface circuit of the access pointsequentially receives one or more frames from the ordered list ofelectronic devices via the communications medium. A processing subsystemin the access point causes the access point to allocate at least twotransmission opportunities within the contention-free period to at leasttwo electronic devices in the ordered list of electronic devices.

In some embodiments, each transmission opportunity within thecontention-free period is adjusted dynamically, as determined andcontrolled by an unscheduled access mechanism implemented within theprocessing subsystem of the access point. According to operation of theunscheduled access mechanism, a start of each transmission opportunityin the at least two transmission opportunities within thecontention-free period is adjusted dynamically by the processingsubsystem based on traffic transmitted via the communications medium. Atransmission opportunity can be terminated by the access point inaccordance with the transmission of an acknowledgment frame thatindicates the access point received at least one frame from acorresponding electronic device. In some embodiments, the processingsubsystem of the access point can limit a duration of each transmissionopportunity to a maximum duration, where a duration of a particulartransmission opportunity can be less than or equal to the maximumduration. In particular, where a first electronic device has respondedto a trigger frame during a first transmission opportunity and theaccess point has transmitted an acknowledgment frame to the firstelectronic device, the access point can indicate a start to a secondtransmission opportunity allocated to a second electronic device bytransmitting a second trigger frame prior to a duration of the firsttransmission opportunity reaching the maximum duration.

In some embodiments, when the access point is configured to utilize theunscheduled access mechanism, each electronic device is configured toenter a low power mode at an end of a corresponding transmissionopportunity allocated to the electronic device and wake up to listen tothe communications medium prior to a start of a next contention-freeperiod. A time associated with the start of the next contention-freeperiod is indicated within the trigger frame.

In some embodiments, each transmission opportunity within thecontention-free period is fixed, as determined and controlled by ascheduled access mechanism implemented within the processing subsystemof the access point. According to operation of the scheduled accessmechanism, a start of each transmission opportunity in the at least twotransmission opportunities within the contention-free period is fixed bythe processing subsystem according to a schedule. In some embodiments,the processing subsystem in the access point can implement a schedulingalgorithm that defines a duration of each transmission opportunitywithin the contention-free period as equal to a duration of thecontention-free period divided by a number of electronic devices in theordered list of electronic devices. The duration of the contention-freeperiod can be pre-defined, such as 2 milliseconds, and the access pointcan periodically define new contention-free periods after a particulartime interval elapses, such as every 5 milliseconds.

In some embodiments, when the access point is configured to utilize ascheduled access mechanism, each electronic device is configured toenter a low power mode at an end of a corresponding transmissionopportunity allocated to the electronic device and wake up to listen tothe communications medium prior to a start of a correspondingtransmission opportunity allocated to the electronic device during anext contention-free period. A time associated with the start of atransmission opportunity allocated to the electronic device during thenext contention-free period can be indicated within the trigger framereceived during a current contention-free period.

In some embodiments, the processing subsystem of the access point isconfigured to cause the interface circuit of the access point tore-transmit the trigger frame to a corresponding electronic deviceappearing first in the ordered list of electronic devices when theaccess point fails to receive a frame of data from the correspondingelectronic device within a threshold time of an end of transmission ofthe trigger frame. In some embodiments, a determination of whether tore-transmit the trigger frame can be based on a comparison of aremaining duration of the current transmission opportunity with aminimum threshold time.

In some embodiments, an electronic device includes: one or more nodesconfigured to communicatively coupled to an antenna, an interfacecircuit communicatively coupled to the one or more nodes, and aprocessing subsystem communicatively coupled to the interface circuit.The interface circuit is configured to cause the electronic device toreceive, from the access point, a trigger frame that includesinformation specifying an ordered list of electronic devices in a set ofelectronic devices that are allowed to transmit data via a firstcommunications medium during a contention-free period and transmit aframe at a temporal position in a sequence of frames from the orderedlist of electronic devices. The processing subsystem is configured tocause the electronic device to: read an identifier positioned first inthe ordered list of electronic devices from the trigger frame; determinethat the identifier is associated with the electronic device; transmitthe frame at the temporal position subsequent to the end of the triggerframe and associated with the communications medium being idle for aperiod of time; identify a time associated with a subsequentcontention-free period; and enter a low power mode subsequent totransmission of the frame.

In some embodiments, the interface circuit is further configured tocause the electronic device to: transmit an advertising packet to theaccess point via a second communications medium associated with awireless personal area network (WPAN); receive, via the secondcommunications medium, a packet of information associated with the WLAN;and receive the trigger frame via the first communications mediumassociated with the WLAN. In some embodiments, the information includesa basic service set identifier (BSSID) for the WLAN and/or informationregarding one or more channels associated with the first communicationsmedium and utilized by the WLAN.

In some embodiments, the first communications medium comprises one ormore channels within a 5 GHz RF spectrum, and the second communicationsmedium comprises one or more channels within a 2.4 GHz radio-frequencyspectrum.

In some embodiments, the period of time that the communications mediumis idle is referred to as a Short Interframe Space (SIFS) having aduration of at least 16 microseconds.

In some embodiments, a wake-up timer of the electronic device is setbased on a time that corresponds to a start of the subsequentcontention-free period. In other embodiments, the wake-up timer of theelectronic device is set based on a time that corresponds to a start ofa corresponding transmission opportunity allocated to the electronicdevice during the subsequent contention-free period as indicated by atimestamp included in the trigger frame.

In some embodiments, a method is described for transmitting a frame froman electronic device configured to communicate with an access point in aWLAN. The method includes, via a processing subsystem of the electronicdevice, reading an identifier positioned first in an ordered list ofelectronic devices included in a trigger frame received, via aninterface circuit of the electronic device, from the access point duringa contention-free period. The method also includes, via the processingsubsystem of the electronic device, determining that the identifier isassociated with the electronic device, and transmitting, subsequent tothe end of the trigger frame and after a period of time during which afirst communications medium associated with the WLAN is idle, a frame tothe access point in response to receiving the trigger frame. The methodalso includes, via the processing subsystem of the electronic device,receiving an acknowledgment frame from the access point, and identifyinga time associated with a subsequent contention-free period as specifiedwithin the trigger frame. The method further includes, via theprocessing subsystem of the electronic device, entering a low power modesubsequent to transmission of the frame. In some embodiments, a wake-uptimer is set based on a time that corresponds with a start time of atransmission opportunity allocated to the electronic device during asubsequent contention-free period, the start time of the transmissionopportunity indicated by a timestamp included in a field of the triggerframe.

In some embodiments, the method further includes transmitting, via theinterface circuit, an advertising packet to the access point via asecond communications medium associated with a WPAN. The method furtherincludes receiving, via the second communications medium, a packet ofinformation associated with the WLAN, wherein the information includes abasic service set identifier for the WLAN. The method also includesreceiving the trigger frame via the first communications mediumassociated with the WLAN. In some embodiments, the WPAN is associatedwith a Bluetooth Low Energy communications protocol.

Other aspects and advantages of the embodiments described above willbecome apparent from the following detailed description, taken inconjunction with the accompanying drawings, which illustrate, by way ofexample, the principles of the described embodiments.

This Summary is provided merely for purposes of summarizing some exampleembodiments so as to provide a basic understanding of some aspects ofthe subject matter described herein. Accordingly, it will be appreciatedthat the above-described features are merely examples and should not beconstrued to narrow the scope of the subject matter described herein inany way. Other features, aspects, and advantages of the subject matterdescribed herein will become apparent from the following DetailedDescription, Figures, and Claims.

BRIEF DESCRIPTION OF THE DRAWINGS

The included drawings are for illustrative purposes and serve only toprovide examples of possible structures and arrangements for thedisclosed systems and techniques for intelligently and efficientlymanaging communication between multiple associated user devices. Thesedrawings in no way limit any changes in form and detail that can be madeto the embodiments by one skilled in the art without departing from thespirit and scope of the embodiments. The embodiments will be readilyunderstood by the following detailed description in conjunction with theaccompanying drawings, wherein like reference numerals designate likestructural elements.

FIG. 1 illustrates a block diagram of an exemplary set of electronicdevices communicating wirelessly in a wireless local area network(WLAN), in accordance with some embodiments.

FIG. 2 illustrates an exemplary protocol for an electronic device toconnect to the WLAN of FIG. 1, in accordance with some embodiments.

FIG. 3 illustrates a trigger frame communicated from the access point toan electronic device 110, in accordance with some embodiments.

FIG. 4 illustrates a data frame communicated between stations of theWLAN, in accordance with some embodiments.

FIG. 5 illustrates an acknowledgment frame communicated between stationsof the WLAN, in accordance with some embodiments.

FIG. 6 illustrates a contention-free end frame communicated from theaccess point to an electronic device, in accordance with someembodiments.

FIG. 7 illustrates an unscheduled access mechanism, in accordance withsome embodiments.

FIG. 8 illustrates an unscheduled access mechanism with retries, inaccordance with some embodiments.

FIG. 9 illustrates a sleep cycle for a number of electronic devicesutilizing the unscheduled access mechanism to communicate via the WLAN,in accordance with some embodiments.

FIG. 10 illustrates a scheduled access mechanism, in accordance withsome embodiments.

FIG. 11 illustrates a scheduled access mechanism with retries, inaccordance with some embodiments.

FIG. 12 illustrates a sleep cycle for a number of electronic devicesutilizing the scheduled access mechanism to communicate via the WLAN, inaccordance with some embodiments.

FIG. 13 illustrates access to the communications medium by multipleWLANs, in accordance with some embodiments.

FIG. 14 presents a flow diagram illustrating an exemplary method forallocating transmission opportunities within a contention-free perioddefined by an access point, in accordance with some embodiments.

FIG. 15 presents a flow diagram illustrating an exemplary method forreducing a power consumption associated with a wireless station, inaccordance with some embodiments.

FIG. 16 presents a flow diagram illustrating an exemplary method forconnecting to a WLAN, in accordance with some embodiments.

FIG. 17 presents a block diagram of an electronic device in accordancewith some embodiments.

Note that like reference numerals refer to corresponding partsthroughout the drawings. Moreover, multiple instances of the same partare designated by a common prefix separated from an instance number by adash.

DETAILED DESCRIPTION

In various embodiments, stations (STAs) connected to a WLAN, includingelectronic devices and/or access points (APs), are configured tocommunicate via a communications medium using a trigger-based accessmechanism. An access point is configured to define a contention-freeperiod associated with the communications medium for transmitting databetween stations. During the contention-free period, the access pointallocates transmission opportunities to each of a number of electronicdevices by transmitting trigger frames to the electronic devicesconnected to the WLAN via the communications medium. Each trigger framecan be directed at a particular electronic device and indicates to thatelectronic device that the current transmission opportunity has beenallocated to that electronic device to transmit data (e.g., frames) tothe access point via the communications medium. A processing subsystemof the access point implements an algorithm, which can be referred to asan access mechanism, for allocating two or more transmissionopportunities within a contention-free period to two or morecorresponding electronic devices connected to the WLAN.

An unscheduled access mechanism is described where the access pointdynamically adjusts a duration of each transmission opportunity withinthe contention-free period based on the traffic on the communicationsmedium. A particular transmission opportunity is allocated to anelectronic device by transmitting a trigger frame that identifies thatelectronic device as a first device in an ordered list of devices. Theelectronic device can respond to the trigger frame by transmitting oneor more data frames to the access point via the communications medium.The access point can then acknowledge receipt of the one or more framesby transmitting an acknowledgment frame to the electronic device,thereby terminating the transmission opportunity allocated to theelectronic device. If the electronic device does not respond to atrigger frame, then the access point can determine whether the triggerframe should be re-transmitted to the electronic device. The duration ofthe transmission opportunity varies according to a number and durationof frames transmitted via the communications medium during thetransmission opportunity as well as delays between frames where thecommunications medium is idle. The access point, via the unscheduledaccess mechanism, can limit the duration of a particular transmissionopportunity to ensure that a minimum number of electronic devicesconnected to the WLAN are allocated at least one transmissionopportunity during the current contention-free period. Furthermore, onceall frames associated with a given electronic device have beentransmitted via the communications medium, the access point can create anew transmission opportunity by sending a trigger frame targeted to adifferent electronic device.

A low power mode can be implemented by stations that are connected tothe WLAN. While utilizing the unscheduled access mechanism, a stationcan enter the low power mode after completion of a transmissionopportunity allocated to the station. Stations can wake up at the startof a next contention-free period to listen to the communications mediumfor additional trigger frames targeted to that station.

A scheduled access mechanism is described where the access pointpre-defines a duration of each transmission opportunity within thecontention-free period. In some cases, the contention-free period issubdivided to provide at least one transmission opportunity to each of anumber of electronic devices connected to the WLAN. Consequently, eachelectronic device is provided with a fixed schedule of time during acontention-free period during which that electronic device can transmitdata via the communications medium.

In some embodiments, the stations can utilize a low power mode moreefficiently when access to the communications medium is controlledaccording to the scheduled access mechanism. For example, electronicdevices can be configured to wake up at a start of a correspondingtransmission opportunity allocated to the electronic device rather thanat the start of the contention-free period. This can allow for theelectronic device to be in the low power mode during both a firstportion of the contention-free period prior to the allocatedtransmission opportunity and a second portion of the contention-freeperiod subsequent to the allocated transmission opportunity.

These and other embodiments are discussed below with reference to FIGS.1-17; however, those skilled in the art will readily appreciate that thedetailed description given herein with respect to these figures is forexplanatory purposes only and should not be construed as limiting.

Note that the communication techniques described herein can be usedduring wireless communication between electronic devices in accordancewith a communication protocol, such as an IEEE 802.11 standard (alsoreferred to as Wi-Fi). For example, the communication technique can beused with IEEE 802.11ax, which is used as an illustrative example in thediscussion that follows. However, this communication technique can alsobe used with a wide variety of other communication protocols, and inaccess points and electronic devices (such as portable electronicdevices or mobile devices) that can incorporate multiple different radioaccess technologies (RATs) to provide connections through differentwireless networks that offer different services and/or capabilities

In particular, an electronic device can include hardware and software tosupport a wireless personal area network (WPAN) according to a WPANcommunication protocol, such as those standardized by the Bluetooth®Special Interest Group (in Kirkland, Wash.) and/or those developed byApple® (in Cupertino, Calif.) that are referred to as an Apple WirelessDirect Link (AWDL). Moreover, the electronic device can communicate via:a wireless wide area network (WWAN), a wireless metro area network(WMAN), a WLAN, near-field communication (NFC), a cellular-telephone ordata network (such as using a third generation (3G) communicationprotocol, a fourth generation (4G) communication protocol, e.g., LongTerm Evolution (LTE), LTE Advanced (LTE-A), a fifth generation (5G)communication protocol, or other present or future developed advancedcellular communication protocol) and/or another communication protocol.In some embodiments, the communication protocol includes a peer-to-peercommunication technique.

The electronic device, in some embodiments, can also operate as part ofa wireless communication system, which can include a set of clientdevices, which can also be referred to as stations (STAs), clientdevices, or client electronic devices, interconnected to an accesspoint, e.g., as part of a WLAN, and/or to each other, e.g., as part of aWPAN and/or an ‘ad hoc’ wireless network, such as a Wi-Fi directconnection. In some embodiments, the client device can be any electronicdevice that is capable of communicating via a WLAN technology, e.g., inaccordance with a WLAN communication protocol. Furthermore, in someembodiments, the WLAN technology can include a Wi-Fi (or moregenerically a WLAN) wireless communication subsystem or radio, and theWi-Fi radio can implement an IEEE 802.11 technology, such as one or moreof: IEEE 802.11a; IEEE 802.11b; IEEE 802.11g; IEEE 802.11-2007; IEEE802.11n; IEEE 802.11-2012; IEEE 802.11ac; IEEE 802.11ax, or otherpresent or future developed IEEE 802.11 technologies.

In some embodiments, the electronic device can act as a communicationshub that provides access to a WLAN and/or to a WWAN and, thus, to a widevariety of services that can be supported by various applicationsexecuting on the electronic device. Thus, the electronic device caninclude an ‘access point’ that communicates wirelessly with otherelectronic devices (such as using Wi-Fi), and that provides access toanother network (such as the Internet) via IEEE 802.3 (which issometimes referred to as ‘Ethernet’).

Additionally, it should be understood that the electronic devicesdescribed herein can be configured as multi-mode wireless communicationdevices that are also capable of communicating via different 3G and/orsecond generation (2G) RATs. In these scenarios, a multi-mode electronicdevice or user equipment (UE) can be configured to prefer attachment toLTE networks offering faster data rate throughput, as compared to other3G legacy networks offering lower data rate throughputs. For example, insome implementations, a multi-mode electronic device is configured tofall back to a 3G legacy network, e.g., an Evolved High Speed PacketAccess (HSPA+) network or a Code Division Multiple Access (CDMA) 2000Evolution-Data Only (EV-DO) network, when LTE and LTE-A networks areotherwise unavailable.

In accordance with various embodiments described herein, the terms‘wireless communication device,’ ‘wireless device,’ ‘electronic device,’‘mobile device,’ ‘mobile station,’ ‘wireless station,’ ‘wireless accesspoint,’ ‘station,’ ‘access point’ and ‘user equipment’ (UE) can be usedherein to describe one or more consumer electronic devices that can becapable of performing procedures associated with various embodiments ofthe disclosure.

FIG. 1 illustrates a block diagram 100 of an example of electronicdevices communicating wirelessly, in accordance with some embodiments.In particular, one or more electronic devices 110 (such as a smartphone,a laptop computer, a notebook computer, a tablet, or another suchelectronic device) and access point 112 communicate wirelessly in aWLAN. Thus, electronic devices 110 are associated with access point 112.For example, electronic devices 110 and access point 112 can wirelesslycommunicate while: detecting one another by scanning wireless channelsin a communications medium such as a subset of the RF spectrum,transmitting and receiving beacons or beacon frames on wirelesschannels, establishing connections (for example, by transmitting connectrequests), and/or transmitting and receiving packets or frames (whichcan include the request and/or additional information, such as data, aspayloads). Note that access point 112 can provide access to a network,such as the Internet, via an Ethernet protocol, and can be a physicalaccess point or a virtual or ‘software’ access point that is implementedby a host on a computer or an electronic device. In some embodiments,the access point 112 can be omitted and a primary electronic device 110can function similar to the access point 112, but without providingaccess via Ethernet or some other wired or wireless protocol to aseparate external network such as the Internet.

As described further below with reference to FIG. 17, electronic devices110 and access point 112 can include subsystems, such as a networkingsubsystem, a memory subsystem, and a processing subsystem. In addition,electronic devices 110 and access point 112 include radios 114 in thenetworking subsystems. More generally, electronic devices 110 and accesspoint 112 can include (or can be included within) any electronic deviceswith networking subsystems that enable electronic devices 110 and accesspoint 112 to wirelessly communicate with another electronic device via acommunications medium, such as one or more channels of a radio frequency(RF) spectrum. This can include transmitting beacon frames on wirelesschannels to enable the electronic devices 110 to make initial contactwith or to detect each other, followed by exchanging subsequentdata/management frames (such as connect requests) to establish aconnection, configure security options (e.g., IPSec), transmit andreceive packets or frames via the connection, etc.

As depicted in FIG. 1, wireless signals 116 (represented by abi-directional jagged line) are communicated by radios 114 in electronicdevice 110-1 and access point 112, respectively. For example, as notedpreviously, electronic device 110-1 and access point 112 can exchangepackets using a communication protocol in a WLAN. For example, accesspoint 112 transmits trigger frames to the one or more electronic devices110. In response, one or more of electronic devices 110 (which aresometimes referred to as a ‘set of electronic devices’) transmit one ormore frames to access point 112. The trigger frame can includeinformation specifying an ordered list of electronic devices in the oneor more electronic devices 110 that are allowed to transmit over thecommunications medium. For example, the information specifying theordered list of electronic devices (such as identifiers of theelectronic devices in the ordered list of electronic devices) can beincluded in dedicated information bytes in a field following a MACheader of the trigger frame.

In response to the trigger frame, the one or more electronic devices 110in the ordered list of electronic devices (such as electronic device110-1) sequentially transmit one or more frames to access point 112 attemporal positions or transmission opportunities that correspond to orare based on the ordered list of electronic devices. For example, agiven electronic device in the ordered list of electronic devices cantransmit a frame in a sequence of one or more frames after another frameis transmitted by a preceding electronic device in the ordered list ofelectronic devices. Alternatively, the given electronic device cantransmit a frame in the sequence of one or more frames during a timeslot after an unused transmit opportunity of the preceding electronicdevice in the ordered list of electronic devices.

In this trigger-based channel-access technique, the given electronicdevice can select a data rate and a length of the frame that ittransmits in response to the trigger frame. For example, the informationin the trigger frame can specify a maximum frame duration, and the framefrom or transmitted by the given electronic device can have a durationthat is less than or equal to the maximum frame duration. Thus, thelengths and/or the data rates of two or more of the frames received fromthe ordered list of electronic devices can be different from each other.For example, each frame can specify data rates of 6 Mbps, 24 Mbps, or 54Mbps depending on the amount of data that needs to be transmitted withina particular frame.

Furthermore, the information in the trigger frame can specify that eachof the electronic devices in the ordered list of electronic devicesresponds to the trigger frame (e.g., by transmitting a frame).Therefore, access point 112 receives a frame from each of the electronicdevices in the ordered list of electronic devices. In some cases, thatframe can be a null frame (e.g., wherein the payload in the framecontains no data). However, in other embodiments, the electronic devicesin the ordered list of electronic devices only transmit at theircorresponding transmission opportunities (which are indirectly specifiedby the ordered list of electronic devices) if they have uplink or queueddata.

After the last electronic device in the ordered list of electronicdevices has transmitted a frame or been allocated a transmissionopportunity, access point 112 can transmit a block acknowledgment to theordered list of electronic devices. However, in other embodiments accesspoint 112 transmits an acknowledgment to each of the electronic devicesin the ordered list of electronic devices after each of the electronicdevices transmits a corresponding frame of data.

Note that access point 112 and at least some of electronic devices 110can be compatible with an IEEE 802.11 standard that includestrigger-based channel access (such as IEEE 802.11ax). However, accesspoint 112 and at least this subset of electronic devices 110 can alsocommunicate with one or more legacy electronic devices that are notcompatible with the IEEE 802.11 standard (e.g., that do not usemulti-user trigger-based channel access). As described further below,the communication technique can also be implemented using a legacyelectronic device.

In addition, note that the transmit power of the electronic devices inthe ordered list of electronic devices can be proportional to a transmitbandwidth of these electronic devices (as opposed to being proportionalor scaling as a number of electronic devices N in the ordered list ofelectronic devices).

In these ways, the communication technique can allow electronic devices110 and access point 112 to reduce contention in the WLAN and to improvecommunication performance (e.g., decrease latency with regard to frametransmission). These capabilities can improve the user experience whenusing electronic devices 110, especially in the context of real-timeapplications.

In the described embodiments, processing a packet or frame in one ofelectronic devices 110 and access point 112 includes: receiving wirelesssignals 116 encoding a packet or a frame; decoding/extracting the packetor frame from received wireless signals 116 to acquire the packet orframe; and processing the packet or frame to determine informationcontained in the packet or frame (such as data in the payload).

In general, the communication via the WLAN in the communicationtechnique can be characterized by a variety of communication-performancemetrics. For example, the communication-performance metric can include:a received signal strength (RSS), a data rate, a data rate forsuccessful communication (which can also referred to as a throughput), alatency, an error rate (such as a retry or resend rate), a mean-squareerror of equalized signals relative to an equalization target,inter-symbol interference, multipath interference, a signal-to-noiseratio (SNR), a width of an eye pattern, a ratio of number of bytessuccessfully communicated during a time interval (such as one to tenseconds) to an estimated maximum number of bytes that can becommunicated in the time interval (the latter of which can also bereferred to as the capacity of a communication channel or link), and/ora ratio of an actual data rate to an estimated data rate (which can alsobe referred to as utilization).

Although we describe the network environment shown in FIG. 1 as anexample, in alternative embodiments, different numbers and/or types ofelectronic devices can be present or otherwise included in the WLAN. Forexample, some embodiments can include more or fewer electronic devices110 connected to the access point 112.

FIG. 2 illustrates a protocol 200 for an electronic device 110 toconnect to the WLAN of FIG. 1, in accordance with some embodiments. Itwill be appreciated that communication via the communications mediumassociated with the WLAN can consume significant energy. For example,operation of the radios 114 can consume energy as data is transmittedvia or received over the wireless communications medium. Therefore, itcan be beneficial to reduce energy consumption by disabling the radio114 or other signal processing circuitry in the electronic device 110for communicating via the WLAN when the electronic device 110 is notconnected to the WLAN. The electronic device 110 can be disconnectedfrom the WLAN when the electronic device 110 is out of range of theaccess point 112 or when the electronic device 110 is initially poweredup. Alternatively, the electronic device 110 can automaticallydisconnect from the WLAN when the electronic device 110 remains idle fora timeout period (e.g., when the electronic device 110 does not transmitdata to the access point 112 for a specified period of time) or underother disconnection criteria, including user input explicitly requestingthe electronic device 110 disconnect from the WLAN.

In some embodiments, the electronic device 110 can be connected to aWPAN that is separate and distinct from the WLAN. For example, theelectronic device 110 can communicate wirelessly with the access point112 via a Bluetooth Low Energy (BLE) communications protocol thatutilizes either the radio 114, or a separate radio, configured tocommunicate via communication channels within the 2.4 GHz RF spectrum.The WPAN communication protocol is designed to reduce energy consumptionof the device when compared to using, e.g., a standard Wi-Ficommunication protocol specified by one or more of the IEEE 802.11standards. The WPAN communication protocol saves energy by reducing thecomplexity of the communication protocol, thereby reducing the datathroughput transmitted over the communication channel. However, thisreduced data throughput can be insufficient for certain applicationsthat require more data throughput or lower latency than the WPANcommunication protocol can provide. Therefore, the electronic device 110can be configured to use the WPAN to communicate with the access point112 in order to connect to the WLAN for wireless communication betweendevices.

As depicted in FIG. 2, the protocol 200 begins at the electronic device110, which can also be referred to as a station, by advertising thepresence of the electronic device 110 on one or more channels of acommunications medium associated with a WPAN. In some embodiments, theelectronic device 110 periodically transmits an advertising packet onone or more channels (e.g., three channels) in the 2.4 GHz RF spectrum.At 204, the access point 112 begins to scan for devices by listening tothe one or more channels for advertising packets. It will be appreciatedthat, in some embodiments, the access point 112 can begin scanning fordevices prior to the electronic device 110 initiating the transmissionof advertising packets at 202. In such cases, the access point 112 canreceive the initial advertising packet transmitted by the electronicdevice 110. Otherwise, as shown in FIG. 2, one or more advertisingpackets is not be received by the access point 112 prior to a particularadvertising packet being received at 206, where the access point 112identifies the electronic device 110 by the payload included in theadvertising packet.

In some embodiments, the advertising packet includes a universallyunique identifier (UUID) that identifies a WPAN interface for theelectronic device 110. The UUID is unique to the electronic device 110and is used to distinguish a particular electronic device 110 from allother electronic devices 110 transmitting advertising packets via theone or more channels associated with the WPAN. In some embodiments, theUUID is a media access control (MAC) address associated with a WPANinterface implemented by the electronic device 110. In some embodiments,the advertising packet can also include one or more advertising datastructures. Each advertising data structure can include a UUID for oneor more services implemented by the electronic device 110. For example,the electronic device 110 can implement a service for connecting to aWLAN that provides low latency, such that the advertising packetindicates to the access point 112 that the electronic device 110 isrequesting a connection with the WLAN.

At 208, the access point 112 transmits connection data to the electronicdevice 110. The connection data can include any data necessary for theelectronic device 110 to connect to the WPAN. At 210, the electronicdevice 110 receives the connection data, which is used to configure theelectronic device 110 to connect to the WPAN. Subsequently, at 212, theaccess point 112 transmits peer-to-peer (P2P) information to theelectronic device 110 via the WPAN, and, at 214, the electronic device110 receives the P2P information.

In some embodiments, the P2P information includes information forestablishing a connection with a WLAN configured to provide low latencyWi-Fi. For example, the P2P information can include a basic service setidentifier (BSSID), a channel or channels associated with the WLAN, andany other parameters necessary to connect to and communicate with theaccess point 112 over the WLAN, such as parameters for implementingIPSec. In some embodiments, the WLAN is established utilizing one ormore channels within a 5 GHz RF spectrum, which is separate and distinctfrom the RF spectrum utilized by the WPAN (e.g., the 2.4 GHz RFspectrum).

At 216, the access point 112 initializes the WLAN. Initialization caninclude configuring the radio 114 to communicate on one or more channelsof the RF spectrum. Initialization can also include adding an identifierfor the electronic device 110 and/or a service implemented by theelectronic device 110 to a data structure stored in a memory of theaccess point 112. The identifier can be utilized by the access point 112to target the electronic device 110. In some embodiments, the identifieris an association identifier (AID) that can be included in the triggerframe to allocate a transmission opportunity over the communicationsmedium to a particular electronic device 110.

At 218, the access point 112 can begin communicating with the electronicdevice 110 according to a trigger-based channel-access technique overthe WLAN. In some embodiments, the trigger-based channel-accesstechnique can be referred to as a Triggered Wi-Fi Access Protocol(TWAP), described in more detail in U.S. patent application Ser. No.15/644,495, which is incorporated herein in its entirety.

At 220, the electronic device 110 initializes the WLAN based on the P2Pinformation received via the WPAN. Initialization can includeconfiguring the radio 114 to communicate on one or more channels of theRF spectrum. Initialization can also include listening for the receiptof one or more trigger frames from the access point 112. It will beappreciated that one or more trigger frames can be transmitted by theaccess point 112 prior to initialization of the WLAN by the electronicdevice 110 at 220. In such cases, the access point 112 will retransmitthe trigger frame until receiving a response from the electronic device110. Alternatively, the electronic device 110 can initialize the WLAN at220 prior to the access point transmitting a trigger frame at 218.

At 222, the electronic device 110 receives the trigger frame. In someembodiments, the trigger frame includes an identifier associated withthe electronic device 110, such as the AID, which indicates that theaccess point 112 has allocated a transmission opportunity for theelectronic device 110 to transmit data on an uplink of the WLAN. At 224,the electronic device 110 transmits one or more frames of station datato the access point 112 via the WLAN. At 226, the access point 112receives the one or more frames of station data. At 228, the accesspoint 112 transmits an acknowledgment (ACK) frame to the electronicdevice 110 via the WLAN to acknowledge receipt of the one or more framesof station data, and, at 230, the electronic device receives the ACKframe. In some embodiments, an ACK frame is transmitted for each frameof station data received from the electronic device 110. In otherembodiments, a single ACK frame is transmitted for multiple frames ofstation data received from the electronic device 110. For example, asingle ACK frame can be transmitted to the electronic device 110 inresponse to a burst of two or more sequential frames of station data toacknowledge receipt of the two or more sequential frames of stationdata.

It will be appreciated that although the WLAN is described as beingimplemented over one or more channels in the 5 GHz RF spectrum, nothingin the detailed description should be construed as limiting allembodiments of the WLAN to be implemented on a particular channel orfrequency range of the RF spectrum. In other embodiments, the WLAN canbe implemented on one or more communication channels in a differentportion of the RF spectrum, such as the 2.4 GHz RF spectrum, a 6 GHz RFspectrum, and the like.

FIG. 3 illustrates a trigger frame 300 communicated from the accesspoint 112 to an electronic device 110, in accordance with someembodiments. In particular, the trigger frame 300 can include a numberof fields. In some embodiments, the trigger frame 300 includes thefollowing fields: a frame control field 302, a duration field 304, areceive address (RA) field 306, a transmit address (TA) field 308, abase timestamp field 310, a slot end timestamp field 312, a next slottimestamp field 314, a trigger options field 316, an AID list lengthfield 318, an AID list field 320, an optional data field 322, and aframe check sequence (FCS) field 324. While example lengths in bytes areprovided in FIG. 3, any/all of the lengths can be modified, and one ormore fields can be added, removed, or modified in other implementations.

Trigger frame 300 can be referred to as a control frame. Note that thetrigger frame 300 specifies an ordered list of electronic devices (e.g.,in AID list field 320) that can use an uplink of the communicationsmedium in the order specified in the AID list field 320. The specificaccess mechanisms utilized to allocate specific transmissionopportunities to each electronic device in the ordered list is describedin more detail below.

In some embodiments, the frame control field 302 is fixed at two bytes.The frame control field 302 can be set to indicate the trigger frame 300is a low latency Wi-Fi trigger frame. The frame control field 302distinguishes a low latency Wi-Fi trigger frame from other types offrames, such as ACK frames or data frames.

In some embodiments, the duration field 304 is fixed at two bytes. Theduration field 304 can be set to indicate a remaining time of acontention-free period associated with the WLAN. As used herein, acontention-free period refers to a set interval where the access point112 is responsible for allocating resource units of the communicationsmedium to various electronic devices 110 connected to the WLAN. In someembodiments, the value of the duration field 304 can be referred to as anetwork allocation vector (NAV) that indicates the remaining time in acontention-free period.

In some embodiments, the RA field 306 and the TA field 308 are fixed atsix bytes. The RA field 306 can be set to a multicast or broadcastaddress of the WLAN such that all electronic devices 110 associated withthe multicast or broadcast address receive the trigger frame 300. The TAfield 308 can be set to the BSSID for the WLAN.

In some embodiments, the base timestamp field 310 is fixed at fourbytes, and the slot end timestamp field 312 and the next slot timestampfield 314 are fixed at two bytes. The base timestamp field 310 includesthe lower 32-bits of the access point 112 timing synchronizationfunction (TSF) at a point in time the trigger frame 300 was generated.The TSF is a timer with modulus 2⁶⁴ (e.g., 64-bit timer) counting inincrements of microseconds (e.g., ticking on 1 MHz clock). Eachelectronic device 110 maintains a separate TSF that is synchronized withthe access point 112 TSF utilizing a timestamp included in periodicbeacon frames transmitted by the access point 112.

In a scheduled access mechanism, as described in more detail below, theslot end timestamp field 312 includes the lower 16-bits of the accesspoint 112 TSF corresponding to the scheduled end of the current uplinkslot associated with the trigger frame 300, and the next slot timestampfield 314 includes the lower 16-bits of the access point 112 TSFcorresponding to the scheduled start of the next scheduled uplink slotfor the first electronic device 110 in the AID list field 320 during thenext contention-free period. In an unscheduled access mechanism, asdescribed in more detail below, the slot end timestamp field 312 and thenext slot timestamp field 314 can be ignored in favor of the durationfield 304, which indicates the end of the current contention-freeperiod.

In some embodiments, the trigger options field 316 is fixed at one byte.The trigger options field 316 can include a number of flags. Forexample, a scheduled trigger flag can be set to one to indicate thetrigger frame 300 is associated with a scheduled access mechanism whereeach electronic device 110 is allocated a fixed slot within thecontention-free period, or the scheduled trigger flag can be set to zeroto indicate the trigger frame 300 is associated with an unscheduledaccess mechanism where each electronic device 110 is triggered in orderas listed in the AID list field 320. The trigger options field 316 canalso include an explicit trigger flag that can be set to one to indicatethat each electronic device 110 included in the AID list field 320 willbe triggered by a separate trigger frame or can be set to zero toindicate multiple electronic devices 110 are triggered, in an order asspecified in the AID list field 320, in response to a single triggerframe. The trigger options field 316 can also include an immediate ACKflag that can be set to one to indicate each uplink packet will beacknowledged by a separate ACK frame or can be set to zero to indicatethat multiple uplink packets can be acknowledged by a single ACK frame.

In some embodiments, the AID list length field 318 is fixed at twobytes. The AID list length field 318 is set to indicate a number ofelectronic devices 110 that are allocated an uplink slot in the currentcontention-free period. It will be appreciated that the value of the AIDlist length field 318 indicates the number of separate and distinctelectronic devices 110 referenced in the AID list field 320.

In some embodiments, the AID list field 320 includes a list of AIDs forone or more electronic devices 110 allocated uplink slots within thecurrent contention-free period. A size of the AID list field 320 isvariable between two and 2N bytes, where N is the number of electronicdevices 110 allocated uplink slots within the current contention-freeperiod.

In some embodiments, an optional data field 322 can include anyadditional data transmitted from the access point 112 to the electronicdevice 110. In some embodiments, the data field 322 can be utilized totransmit feedback information to an electronic device 110. For example,the access point 112 can transmit haptic data to an electronic device110 within the trigger frame 300. The data field 322 can be used forvarious purposes but is typically limited in size, e.g., less than 20bytes. More substantial information passed between the access point 112and the electronic device 110 can be transmitted within a separate dataframe, as discussed below.

In some embodiments, the FCS field 324 is fixed at four bytes. The FCSfield 324 contains an error-detecting code that is added to the end ofthe trigger frame 300. The value contained in the FCS field 324 iscalculated based on the values in one or more other fields of the frame,such as the frame control field 302, the duration field 304, the RAfield 306, and so forth. Receiving stations can check the integrity ofthe received trigger frame 300 by checking the value in the FCS field324 against a value calculated from the values in one or more otherfields in the received trigger frame 300.

It will be appreciated that, in other embodiments, the format of thetrigger frame 300 can be different than the format set forth above. Forexample, the AID list length can be fixed at N devices and the AID listlength field 318 can be omitted from the trigger frame 300. As anotherexample, the FCS field 324 can be omitted where the communicationsprotocol does not implement error checking. In some embodiments, theorder of the fields in the frame can be changed. For example, thetrigger options field 316 can be ordered after the data field 322.

FIG. 4 illustrates a data frame 400 communicated between stations of theWLAN, in accordance with some embodiments. In particular, the data frame400 can include a number of fields. In some embodiments, the data frame400 includes the following fields: a frame control field 402, a durationfield 404, a first address (A1) field 406, a second address (A2) field408, a third address (A3) field 410, a sequence control field 412, aQuality of Service (QoS) control field 414, a data field 416, and aframe check sequence (FCS) field 418. While example lengths in bytes areprovided in FIG. 4, any/all of the lengths can be modified, and one ormore fields can be added, removed, or modified in other implementations.

In some embodiments, the frame control field 402 is fixed at two bytes.The frame control field 402 can be set to indicate the data frame 400includes a data payload and to differentiate the data frame from othercontrol and management frames such as RTS/CTS frames, ACK frames, andthe like.

In some embodiments, the duration field 404 is fixed at two bytes. Theduration field 404 can be set to a fixed value, e.g., 32767 when thedata frame 400 is transmitted within a contention-free period. In otherembodiments, the duration field 404 can be set to a value that indicatesthe length of the data frame 400.

In some embodiments, the address fields, e.g., the A1 field 406, the A2field 408, and the A3 field 410 are fixed at six bytes. The A1 field 406can be set to destination address (DA), the A2 field 408 can be set tothe source address (SA), and the A3 field 410 can be set to the BSSIDfor the WLAN. The address fields can take the form of conventional IEEE802.11 MAC addresses.

In some embodiments, the sequence control field 412 is fixed at twobytes. The sequence control field 412 includes a sequence number andfragment number for a sequence of data frames. The sequence controlfield 412 can be used in a burst mode where multiple data frames aresent in order prior to receiving an ACK frame in response.

In some embodiments, the QoS control field 414 is fixed at two bytes.The QoS control field 414 includes parameters related to providing QoSfor a data stream of one or more data frames. The parameters can includea QoS type (e.g., video, audio, etc.), a priority value, as well asother parameters for implementing a QoS algorithm.

In some embodiments, a data field 416 can include any data transmittedfrom one station to another station. The data field 416 is variablesize, but can be limited at the upper end by a maximum size of a frametransmitted over the communications medium minus the number of bytes forthe MAC header and MAC footer (e.g., FCS field 418).

In some embodiments, the FCS field 418 is fixed at four bytes. The FCSfield 324 contains an error-detecting code that is added to the end ofthe data frame 400. The value contained in the FCS field 324 iscalculated based on the values in one or more other fields of the dataframe, such as the frame control field 402, the duration field 404, theaddress fields 406/407/408, and so forth. Receiving stations can checkthe integrity of the received data frame by checking the value in theFCS field 418 against a value calculated from the values in one or moreother fields in the received data frame.

FIG. 5 illustrates an acknowledgment (ACK) frame 500 communicatedbetween stations of the WLAN, in accordance with some embodiments. Inparticular, the ACK frame 500 can include a number of fields. In someembodiments, the ACK frame 500 includes the following fields: a framecontrol field 502, a duration field 504, a receive address (RA) field506, and a FCS field 508. While example lengths in bytes are provided inFIG. 5, any/all of the lengths can be modified, and one or more fieldscan be added, removed, or modified in other implementations.

In some embodiments, the frame control field 502 is fixed at two bytes.The frame control field 502 can be set to indicate the ACK frame 500 isan acknowledgment of successful receipt of a previously transmittedframe transmitted over the communications medium by a station.

In some embodiments, the duration field 504 is fixed at two bytes. Theduration field 504 can be set to a fixed value, e.g., 32767 when the ACKframe 500 is transmitted within a contention-free period. In otherembodiments, the duration field 504 can be set to a value that indicatesthe length of the ACK frame 500.

In some embodiments, the RA field 506 is fixed at six bytes. The RAfield 506 includes an 802.11 MAC address for the station that sent theframe being acknowledged.

In some embodiments, the FCS field 508 is fixed at four bytes. The FCSfield 508 contains an error-detecting code that is added to the end ofthe ACK frame 500. The value contained in the FCS field 508 iscalculated based on the values in one or more other fields of the ACKframe 500, such as the frame control field 502, the duration field 504,and the RA field 506. Receiving stations can check the integrity of thereceived ACK frame 500 by checking the value in the FCS field 508against a value calculated from the values in one or more other fieldsin the received ACK frame 500.

In some embodiments, the format of the ACK frame 500 can also be used asa clear-to-send (CTS) frame, where the frame control field 502 includesa different value that indicates the frame is a CTS frame instead of anACK frame.

FIG. 6 illustrates a contention-free end (CF-END) frame 600 communicatedfrom the access point 112 to an electronic device 110, in accordancewith some embodiments. In particular, the CF-END frame 600 can include anumber of fields. In some embodiments, the CF-END frame 600 includes thefollowing fields: a frame control field 602, a duration field 604, areceive address (RA) field 606, a transmit address (TA) field 608, andan FCS field 610. While example lengths in bytes are provided in FIG. 6,any/all of the lengths can be modified, and one or more fields can beadded, removed, or modified in other implementations.

In some embodiments, the frame control field 602 is fixed at two bytes.The frame control field 602 can be set to indicate the CF-END frame 600identifies the end of the contention-free period.

In some embodiments, the duration field 604 is fixed at two bytes. Theduration field 604 can be set to a fixed value, e.g., 32767 when theCF-END frame 600 is transmitted within a contention-free period. Inother embodiments, the duration field 604 can be set to a value thatindicates the length of the CF-END frame 600.

In some embodiments, the RA field 606 and the TA field 608 are fixed atsix bytes. The RA field 606 can be set to a multicast or broadcastaddress of the WLAN such that all electronic devices 110 associated withthe multicast or broadcast address receive the CF-END frame 600. The TAfield 608 can be set to the BSSID for the WLAN.

In some embodiments, the FCS field 608 is fixed at four bytes. The FCSfield 608 contains an error-detecting code that is added to the end ofthe CF-END frame 600. The value contained in the FCS field 608 iscalculated based on the values in one or more other fields of the CF-ENDframe 600, such as the frame control field 602, the duration field 604,the RA field 606, and the TA field 608. Receiving stations can check theintegrity of the received CF-END frame 600 by checking the value in theFCS field 608 against a value calculated from the values in one or moreother fields in the received CF-END frame 600.

In some embodiments, the format of the CF-END frame 600 can also be usedas a request-to-send (RTS) frame, where the frame control field 602includes a different value that indicates the frame is a RTS frameinstead of a CF-END frame.

In some embodiments, each electronic device 110 can transmit an RTSframe to the access point 112 prior to transmitting a data frame via thecommunications medium. In such embodiments, the electronic device 110will confirm receipt of a corresponding CTS frame from the access point112 prior to sending the data frame.

Several contention-free access mechanisms utilized by the WLAN are nowdescribed. During the communication technique, the access point cantransmit a trigger frame via the communications medium in order toallocate an uplink slot (e.g., a transmission opportunity) during acontention-free period to a particular electronic device. The electronicdevices can transmit data via the communications medium during theirallocated transmission opportunity if they have buffered or queued data.Otherwise, an electronic device can elect not to transmit on the uplinkduring the allocated transmission opportunity. When that occurs, thenext electronic device in the ordered list of electronic devices can beallocated the next transmission opportunity.

The WLAN is managed by the access point 112. Management of the WLAN caninclude allocating resource units of the communications medium, managingconnections to the WLAN, monitoring the communications medium forinterference from other signals, and so forth. The AP 112 specificallyallocates resource units of the communications medium, via thetransmission of trigger frames, to particular electronic devices 110 totransmit via the communications medium according to a contention-freeaccess mechanism.

FIG. 7 illustrates a diagram 700 of an unscheduled access mechanism, inaccordance with some embodiments. The unscheduled access mechanismrefers to an algorithm, implemented by the processing subsystem of theaccess point, where the duration of a transmission opportunity is notpre-defined by the access point. Instead, a start of each transmissionopportunity in at least two transmission opportunities within thecontention-free period is adjusted dynamically by the processingsubsystem based on traffic transmitted via the communications medium.

According to operation of the unscheduled access mechanism, the accesspoint 112 determines an order of a number of transmission opportunitiesin a particular contention-free period allocated to one or moreelectronic devices 110 connected to the WLAN. The access point 112 thentransmits trigger frames over the communications medium according to theorder, allowing the various electronic devices 110 connected to the WLANto transmit data to the access point 112 in one or more frames.

As depicted in FIG. 7, at the start of a contention-free period, theaccess point 112 transmits a first trigger frame 712 to a firstelectronic device 110-1. In response to the first trigger frame 712, thefirst electronic device 110-1 transmits a frame of station data 722 tothe access point 112 after a specified delay. In some embodiments, thedelay utilized by the unscheduled access medium has a duration of 16microseconds (μs) and can be referred to as a Short Interframe Space(SIFS), which is utilized for high-priority transmissions in othercontention-based protocols. In other embodiments, the delay can beincreased or decreased (e.g., the delay can be 10 μs). Upon receivingthe frame of station data 722 and after a delay (e.g., SIFS), the accesspoint 112 transmits an ACK frame 732 to the first electronic device110-1. The ACK frame 732 indicates the end of the transmissionopportunity allocated to the first electronic device 110-1.

After a delay (e.g., SIFS) and at the start of a second transmissionopportunity, the access point 112 transmits a second trigger frame 714to a second electronic device 110-2. In response to the second triggerframe 714, the second electronic device 110-2 transmits a frame ofstation data 724 to the access point 112 after a specified delay. Uponreceiving the frame of station data 724 and after a delay (e.g., SIFS),the access point 112 transmits an ACK frame 734 to the second electronicdevice 110-2. The ACK frame 734 indicates the end of the secondtransmission opportunity allocated to the second electronic device110-2.

After a delay (e.g., SIFS) and at the start of a third transmissionopportunity, the access point 112 transmits a third trigger frame 716 toa third electronic device 110-3. In response to the third trigger frame716, the third electronic device 110-3 transmits a frame of station data726 to the access point 112 after a specified delay. Upon receiving theframe of station data 726 and after a delay (e.g., SIFS), the accesspoint 112 transmits an ACK frame 736 to the third electronic device110-6. The ACK frame 736 indicates the end of the third transmissionopportunity allocated to the second electronic device 110-3.

After a delay (e.g., SIFS) and at the start of a fourth transmissionopportunity, the access point 112 transmits a fourth trigger frame 718to a fourth electronic device 110-4. In response to the fourth triggerframe 718, the fourth electronic device 110-4 transmits a frame ofstation data 728 to the access point 112 after a specified delay. Uponreceiving the frame of station data 728 and after a delay (e.g., SIFS),the access point 112 transmits an ACK frame 738 to the fourth electronicdevice 110-4. The ACK frame 738 indicates the end of the fourthtransmission opportunity allocated to the fourth electronic device110-4.

The access point 112 can continue sending trigger frames and receivingframes of station data for zero or more additional electronic devices110 connected to the WLAN in accordance with the order determined by theaccess point 112. Once all transmission opportunities have beenallocated to the electronic devices 110 connected to the WLAN, theaccess point 112 transmits a CF-END frame 742 indicating the end of thecontention-free period. The number of transmission opportunities thatare available within a particular contention-free period depends on aduration of the contention-free period, the size and/or data rateassociated with each of the frames transmitted during each transmissionopportunity, a maximum size of a frame (e.g., maximum size of the frameof station data), and so forth. Consequently, in the unscheduled accessmechanism, the total number of transmission opportunities within a fixedcontention-free period is unknown at the start of the contention-freeperiod.

FIG. 8 illustrates a diagram 800 of an unscheduled access mechanism withretries, in accordance with some embodiments. In some cases, aparticular electronic device 110 can fail to send station data to theaccess point 112 in response to a trigger frame. In some cases, anelectronic device 110 can fail to receive a trigger frame. This failurecan be caused by, among other reasons, interference on thecommunications medium, inadequate signal strength, and the like. Inother cases, the electronic device 110 can receive the trigger frame;however, the electronic device 110 can determine that there is nobuffered or queued data to send to the access point 112. In yet othercases, the electronic device 110 can attempt to transmit the stationdata to the access point 112; however, the access point 112 can fail toreceive the station data due to, e.g., interference, inadequate signalstrength, and the like.

In some cases, the access point 112 can be configured to perform anumber of retries when a particular electronic device 110 fails torespond to a trigger frame. As depicted in FIG. 8, the access point 112can wait for a specified time after transmission of the trigger frame toreceive a response from the electronic device 110. If a response (e.g.,a frame of station data) is not received within the specified time, thenthe access point 112 can attempt to re-transmit the trigger frame. Insome cases, re-transmitting the trigger frame will result in receipt ofthe frame of station data from the electronic device (as illustratedduring the transmission opportunity allocated to the first electronicdevice 110-1), at which point an ACK frame is transmitted to theelectronic device 110. In other cases, re-transmitting the trigger framewill not result in the receipt of the frame of station data from theelectronic device (as illustrated during the transmission opportunityallocated to the second electronic device 110-2), where no ACK frame istransmitted to the electronic device and, instead, a new trigger frameassociated with a new transmission opportunity can be transmitted to adifferent electronic device 110.

It will be appreciated that, in various embodiments, the number of retryattempts implemented by the access point 112 during each transmissionopportunity can be dynamically set at zero or more. In some embodiments,the number of retries can be set based on the number of electronicdevices connected to the WLAN. It will be appreciated that failures andsubsequent retries can increase the duration of a particulartransmission opportunity within the contention-free period. A largenumber of failures and subsequent retries can mean fewer transmissionopportunities can be allocated within a particular contention-freeperiod of fixed length. Consequently, an access point cannot guaranteethat all electronic devices 110 are allocated a transmission opportunitywithin the contention-free period before the expiration of thecontention-free period (e.g., before expiration of the NAV set in theduration field 304 of the trigger frame 300). In some embodiments, eachtransmission opportunity is associated with a maximum duration, and aduration of a particular transmission opportunity can be less than orequal to the maximum duration. Consequently, the access point canguarantee that a minimum number of electronic devices 110 are allocateda transmission opportunity within the contention-free period.

A major problem with contention-based access mechanisms implemented inlegacy Wi-Fi is that Quality of Service (QoS) cannot be ensured due tothe variable latency associated with the contention-based accessmechanisms. In contrast, low latency Wi-Fi can be implemented bylimiting the duration of the contention-free period and allocatingtransmission opportunities to electronic devices 110 according to a dutycycle associated with a series of contention-free periods. For example,in some embodiments, the access point 112 sets the contention-freeperiod to have a duration of 2 ms. A number of transmissionopportunities can be allocated to one or more electronic devices 110within the contention-free period, followed by a number of additionaltransmission opportunities allocated to the one or more electronicdevices 110 in a subsequent contention-free period.

In some embodiments, QoS can be provided to at least one electronicdevice 110 by prioritizing the at least one electronic device 110 withinthe order of electronic devices 110 listed in the AID list field 320 ofa trigger frame 300. In some cases, a maximum size of a frame along withknowledge of the number of allowed retries per transmission opportunityand an order and type of frames transmitted during a transmissionopportunity as well as a duration of the contention-free period candetermine a minimum number of transmission opportunities percontention-free period. The minimum number of transmission opportunitiescan represent a number of electronic devices 110 for which a particularQoS can be ensured utilizing the unscheduled access mechanism. In thismanner, low latency Wi-Fi can be provided for real-time applicationssuch as streaming video, audio, gaming, and the like.

In some embodiments, the individual stations might benefit from reducedpower consumption when configured to communicate with the WLAN accordingto the aforementioned communication techniques. In such embodiments, thestations can advantageously enter a low-power mode during at least aportion of the contention-free period in order to reduce powerconsumption of the electronic device 110.

In some embodiments, each trigger frame 300 transmitted by the accesspoint 112 includes an AID list field 320 indicating the electronicdevices 110 that will be allocated a transmission opportunity, ifsufficient resource units are available, within the contention-freeperiod. The trigger frames 300 transmitted by the access point 112 alsoinclude an indication of the end of the current contention-free period,relative to the base timestamp field 310, in the duration field 304.Consequently, each electronic device 110 can inspect the AID list field320 to determine if an AID associated with that particular electronicdevice 110 is listed in the AID list field 320. If the corresponding AIDfor that electronic device 110 is not included in the AID list field 320of the trigger frame 300, then the electronic device 110 can enter thelow power mode until the end of the current contention-free period. Insome embodiments, the low power mode includes disabling the radio 114and/or signal processing circuitry associated with the physical layer ofthe WLAN.

FIG. 9 illustrates a diagram 900 of a sleep cycle for a number ofelectronic devices utilizing the unscheduled access mechanism tocommunicate via the WLAN, in accordance with some embodiments. Allelectronic devices 110 connected to the WLAN should wake up at thebeginning of the contention-free period 910 and listen to thecommunications medium to receive trigger frames 300.

As depicted in FIG. 9, at the beginning of the contention-free period910, a first trigger frame 712, transmitted by the access point 112,allocates a first transmission opportunity to a first electronic device110-1. The first electronic device 110-1 responds to the first triggerframe 712 by transmitting a frame of station data 722 to the accesspoint 112. The access point 112 then transmits an ACK frame 732 to thefirst electronic device 110-1, ending the first transmissionopportunity. Once the first transmission opportunity is concluded, thefirst electronic device 110-1 can enter a low power mode, sometimesreferred to as a sleep mode. Prior to entering the low power mode, thefirst electronic device 110-1 can calculate a wake-up time, relative toa value of the TSF of the first electronic device 110-1, correspondingto the start of the next contention-free period. The first electronicdevice 110-1 can be configured to exit the low power mode at or prior tothe wake-up time. In some embodiments, an electronic device 110 can seta wake-up timer based on the wake-up time that corresponds to a start ofthe subsequent contention-free period. The expiration of the wake-uptimer is configured to trigger an operation to exit the low power mode.

The other electronic devices 110 remains awake during the firsttransmission opportunity to await the next trigger frame 300. At thebeginning of the second transmission opportunity, a second trigger frame714, transmitted by the access point 112, allocates a secondtransmission opportunity to a second electronic device 110-2. The secondelectronic device 110-2 responds to the second trigger frame 714 bytransmitting a frame of station data 724 to the access point 112. Theaccess point 112 then transmits an ACK frame 734 to the secondelectronic device 110-2, ending the second transmission opportunity.Once the second transmission opportunity is concluded, the secondelectronic device 110-2 can enter the low power mode. Prior to enteringthe low power mode, the second electronic device 110-2 can calculate awake-up time, relative to a value of the TSF of the second electronicdevice 110-2, corresponding to the start of the next contention-freeperiod. The second electronic device 110-2 can be configured to exit thelow power mode at or prior to the wake-up time.

The third electronic device 110-3 and the fourth electronic device 110-4similarly enter a low power mode subsequent to the conclusion of acorresponding transmission opportunity allocated to the third electronicdevice 110-3 or the fourth electronic device 110-4, respectively. Itwill be appreciated that the ratio of an awake period to a sleep periodfor each electronic device 110 depends on a position of the transmissionopportunity allocated to the corresponding electronic device 110 duringthe contention-free period 910. For example, a ratio of the awake periodto sleep period for the first electronic device 110-1 is lower than theratio of the awake period to sleep period for the fourth electronicdevice 110-4. Consequently, power consumption of the fourth electronicdevice 110-4 is typically greater than the power consumption of thefirst electronic device 110-1, all other things being equal (e.g., theamount of data transmitted via the WLAN, transmission power, etc.).

In some embodiments, the access point 112 is configured to mitigateuneven power consumption effects by adjusting the order of thetransmission opportunities allocated to the various electronic devices110 during a number of contention-free periods according to around-robin schedule. For example, during a first contention-freeperiod, the order of electronic devices 110 can be selected as 110-1,110-2, 110-3, and 110-4; during a second contention-free period, theorder of electronic devices 110 can be selected as 110-2, 110-3, 110-4,and 110-1; during a third contention-free period, the order ofelectronic devices 110 can be selected as 110-3, 110-4, 110-1, and110-2; and during a fourth contention-free period, the order ofelectronic devices 110 can be selected as 110-4, 110-1, 110-2, and110-3. Consequently, this round-robin scheduling ensures that, onaverage over a number of contention-free periods, the ratio of awakeperiod to sleep period for all electronic devices is approximatelysimilar.

The ability to sleep between transmission opportunities allocated to aparticular electronic device 110 can be instrumental in saving power andextending the battery life of mobile devices. The unscheduled accessmechanism described above is not conducive to absolute efficiency whendetermining when an electronic device 110 can enter the low power modeand when the electronic device 110 needs to wake up. Due to the natureof the unscheduled access mechanism, each electronic device is onlyaware, a priori, when the next contention-free period is scheduled tobegin and whether the access point 112 will attempt to allocate atransmission opportunity to the electronic device 110 during the currenttransmission opportunity. This means that the electronic device 110 mustremain awake and listen to the communications medium for a trigger frametargeted at that device, even during a duration of one or more othertransmission opportunities allocated to different electronic devices110.

FIG. 10 illustrates a diagram 1000 of a scheduled access mechanism, inaccordance with some embodiments. The scheduled access mechanism refersto an access mechanism where a start of each transmission opportunity inthe at least two transmission opportunities within the contention-freeperiod is fixed by the processing subsystem of the access point 112according to a schedule. In some embodiments, the schedule is determinedprior to the start of each contention-free period. In some embodiments,a duration of each transmission opportunity within the contention-freeperiod is set equal to a duration of the contention-free period dividedby a number of electronic devices in the ordered list of electronicdevices. In other embodiments, a duration of each transmissionopportunity within the contention-free period can be set based on a QoStype or priority value associated with each electronic device of anumber of electronic devices. For example, a larger transmissionopportunity can be granted to a video QoS type than an audio QoS type.Nevertheless, the duration of each transmission opportunity is fixed atthe start of a contention-free period and is not adjusted dynamicallybased on the traffic transmitted via the communications medium.

According to the scheduled access mechanism, the access point 112determines an order of a number of transmission opportunities in aparticular contention-free period allocated to one or more electronicdevices 110 connected to the WLAN. The access point 112 is configured todivide the contention-free period into a number of discrete transmissionopportunities that are allocated to particular electronic devices 110 atspecific times within the contention-free period. The access point 112then transmits trigger frames over the communications medium accordingto the order and at the specific times, allowing the various electronicdevices 110 connected to the WLAN to transmit station data to the accesspoint 112 during a corresponding transmission opportunity.

In other words, as depicted in FIG. 10, at the start of acontention-free period, the access point 112 transmits a first triggerframe 1012 to a first electronic device 110-1 at the beginning of afirst transmission opportunity 1052. In response to the first triggerframe 1012, the first electronic device 110-1 transmits a frame ofstation data 1022 to the access point 112 after a specified delay. Uponreceiving the frame of station data 1022 and after the delay (e.g.,SIFS), the access point 112 transmits an ACK frame 1032 to the firstelectronic device 110-1. Unlike in the unscheduled access mechanism,described above, the ACK frame 1032 does not indicate the end of thefirst transmission opportunity 1052 allocated to the first electronicdevice 110-1. Again, a duration of the first transmission opportunity1052 is pre-defined by the access point 112 and, therefore, even thoughthe first electronic device 110 has finished transmitting the stationdata and received an acknowledgment from the access point 112 at a firsttime during the first transmission opportunity 1052, the access point112 waits until the start of the second transmission opportunity 1054 tosend then second trigger frame 1014 to the second electronic device110-2.

At the start of the second transmission opportunity 1054, the accesspoint 112 transmits a second trigger frame 1014 to a second electronicdevice 110-2. In response to the second trigger frame 1014, the secondelectronic device 110-2 transmits a frame of station data 1024 to theaccess point 112 after a specified delay. Upon receiving the frame ofstation data 1024 and after the delay (e.g., SIFS), the access point 112transmits an ACK frame 1034 to the second electronic device 110-2.Again, the access point 112 waits until subsequent transmissionopportunities to send additional trigger frames to one or moreadditional electronic devices 110. Following all scheduled transmissionopportunities, the access point 112 transmits a CF-END frame 1042 toindicate the end of the contention-free period.

It will be appreciated that the information identifying the pre-definedduration of the transmission opportunities can be supplied to theelectronic devices 110 within the trigger frame. In some embodiments,the access point 112 populates or generates the fields of the triggerframe, including: a NAV value in the duration field 304 indicating thetime remaining in the contention-free period, a value (e.g., timestamp)corresponding to the start of the current transmission opportunity inthe base timestamp field 310, and a value (e.g., timestamp)corresponding to the end of the current transmission opportunity in theslot end timestamp field 312. The electronic device 110 can read thesefields from the trigger frame to determine how much time is available tosend data during the currently allocated transmission opportunity.

In some embodiments, the electronic device 110 can adjust the payloadincluded in the frame of station data based on the duration of thetransmission opportunity. For example, the size of the payload can beadjusted to fit within the transmission opportunity and allow the accesspoint 112 to send an ACK frame to the electronic device 110. Anytruncated data can be queued or buffered to be transmitted during thenext transmission opportunity. Alternatively, in some embodiments, theheader for the frame of station data can include a field that indicatesthe station has buffered data that needs to be sent such that the accesspoint 112 can allocate an additional transmission opportunity to theelectronic device 110 during the next contention-free period. Forexample, an additional transmission opportunity (e.g., two transmissionopportunities) can be allocated to the same electronic device 110 duringa subsequent contention-free period.

In other embodiments, the electronic device 110 can adjust a data rateassociated with a fixed payload size to ensure that the frame of stationdata can be transmitted within the currently allocated transmissionopportunity. For example, the electronic device 110, can change themodulation and coding scheme (MCS) used to transmit the frame of stationdata based on the duration of the transmission opportunity. The selectedMCS can be set in the preamble or header of the frame using a code in afield of the preamble or header. Higher data rates will enable more datato be transmitted in a shorter duration of the transmission opportunity,but at the cost of potential interference causing a failure at theaccess point 112 to receive the frame of station data. It will beappreciated that the algorithm for selecting the MCS based on theduration of the allocated transmission opportunity can take intoconsideration additional criteria such as: a size of the queued data tobe encoded within the frame payload, whether one or more retries withinthe transmission opportunity are enabled or disabled, historicalinformation related to the success or failure of previous frametransmissions, and the like.

It will also be appreciated that the delay between the ACK frame 1032and the start of the second transmission opportunity 1054 represents anidle communications medium. Where the delay is significantly longer thanthe SIFS, stations of other WLANs using the same communications mediumwith a contention-based access mechanism such as CSMA/CA could transmitover the communications medium prior to the start of the nexttransmission opportunity allocated within the WLAN. In other words,there is no guarantee that the communications medium will be idle at thestart of the second transmission opportunity when the delay between theACK frame 1032 and the trigger frame 1014 is large. In such cases, theaccess point 112 delays the sending of the second trigger frame 1014until the communications medium is idle for a minimum delay (e.g., theSIFS). In other words, the trigger frame 1014 can be delayed whilewaiting for traffic from other WLANs to finish transmission on thecommunications medium.

This delay is immaterial as long as the trigger frame is transmittedprior to the end of the current transmission opportunity and there is asufficient amount of time left before the end of the transmissionopportunity to transmit a frame of station data and receive an ACK framefrom the access point 112. In some embodiments, if the trigger frame isreceived by the electronic device 110 and the electronic device 110determines that the time between the trigger frame and the end of thetransmission opportunity is smaller than a minimum time threshold tosend data and receive the ACK frame, then the electronic device 110 canignore the trigger frame and wait for the next transmission opportunityto be allocated to the electronic device 110 by the access point 112.

FIG. 11 illustrates a diagram 1100 of a scheduled access mechanism withretries, in accordance with some embodiments. In some embodiments, theaccess point 112 can be configured to perform a number of retries withina scheduled transmission opportunity when a particular electronic device110 fails to respond to a trigger frame. As depicted in FIG. 11, theaccess point 112 can wait for a specified time after transmission of thetrigger frame to receive a response from the electronic device 110. If aresponse (e.g., a frame of station data) is not received within thespecified time, then the access point 112 can attempt to re-transmit thetrigger frame. In some cases, re-transmitting the trigger frame willresult in receipt of the frame of station data from the electronicdevice (as illustrated as trigger frames 1012-1 and 1012-2 transmittedduring the first transmission opportunity 1052 allocated to the firstelectronic device 110-1), at which point an ACK frame is transmitted tothe electronic device 110. In other cases, re-transmitting the triggerframe will not result in the receipt of the frame of station data fromthe electronic device (as illustrated during the transmissionopportunity allocated to the second electronic device 110-2), where noACK frame is transmitted to the electronic device and, instead, a newtrigger frame associated with a new transmission opportunity can betransmitted to a different electronic device 110. The trigger frame canbe re-transmitted two or more times during a particular transmissionopportunity (as illustrated as trigger frames 1012-1 and 1012-2transmitted during the first transmission opportunity 1052 allocated tothe first electronic device 110-1).

It will be appreciated that, in various embodiments, the number of retryattempts implemented by the access point 112 during each transmissionopportunity can be dynamically adjusted based on the duration of thecurrent transmission opportunity. In some embodiments, the number ofretries can be set based on a minimum time that is required to receivestation data from the electronic device 110 and also send an ACK frameto the electronic device 110. The access point 112 can compare the timeremaining in the current transmission opportunity with the minimum timein order to determine whether enough time is available to make anotherattempt to trigger the station. Thus, retries are enabled only if thereis adequate time left within a transmission opportunity to attempt theretry. For example, if an ACK frame takes approximately 25 microsecondsto transmit, a frame of station data takes approximately 50 microsecondsto transmit, and each delay between frames is, e.g., 16 microseconds,then approximately 140 microseconds after the trigger frame is requiredto wait a delay, receive the station data, wait a delay, send the ACKframe and wait a delay before the start of the next transmissionopportunity to send the next trigger frame. Consequently, a thresholdtime of, e.g., 200 microseconds can be required to remain within thecurrent transmission opportunity in order to transmit a subsequenttrigger frame as part of a retry attempt.

It will be appreciated that the duration of the transmissionopportunities can be set based on the number of electronic devices 110connected to the WLAN. For example, the contention-free period can befixed at, e.g., 3 milliseconds. If there are eight electronic devices110 connected to the WLAN, then each transmission opportunity can be setat 375 microseconds. Thus, whether retries are enabled within thescheduled access mechanism can be dependent on the number of electronicdevices 110 connected to the WLAN because the duration of thetransmission opportunity provided to each electronic device 110 can beshorter when more devices are connected to the WLAN.

In some embodiments, the duration of transmission opportunities can befixed (e.g., 300 microseconds), which limits the number of transmissionopportunities available within a contention-free period. However, if thecontention-free period includes more transmission opportunities than thenumber of electronic devices 110 connected to the WLAN, then the accesspoint can reserve one or more transmission opportunities within thecontention-free period to allow for retry attempts to unresponsiveelectronic devices 110. In such cases, the electronic devices 110 can beincluded in the AID list field 320 multiple times in the trigger framesat the start of the contention-free period in order to force theelectronic devices 110 to stay away for the subsequent transmissionopportunity. Then, when an unassigned transmission opportunity isreached, the access point 112 can re-assign that transmissionopportunity dynamically on an as-needed basis. For example, thetransmission opportunity can be assigned in response to a failure toreceive station data from a particular electronic device 110 during apreceding transmission opportunity within the current contention-freeperiod. As another example, the transmission opportunity can be assignedin response to a flag set in the station data received during apreceding transmission opportunity. For example, an electronic device110 can indicate that there is additional queued or buffered stationdata that is waiting to be transmitted to the access point 112. Theaccess point 112 can then allocate one of the extra transmissionopportunities within the contention-free period to that particularelectronic device 110.

In some embodiments, the individual stations can benefit from reducedpower consumption when configured to communicate with the WLAN accordingto the aforementioned communication techniques. In such embodiments, thestations can advantageously enter a low-power mode during at least aportion of the contention-free period in order to save power.

In some embodiments, each trigger frame 300 transmitted by the accesspoint 112 includes a base timestamp field 310 that indicates the currentvalue of the TSF maintained by the access point 112 corresponding with atime matching the generation of the trigger frame 300. The value in thebase timestamp field 310 should be synchronized to a value of the TSFmaintained by the electronic device 110. The trigger frames 300transmitted by the access point 112 also include an indication of theend of the current contention-free period, relative to the basetimestamp field 310, in the duration field 304, an indication of the endof the current transmission opportunity in the slot end timestamp field312, and an indication of a start of the next transmission opportunityallocated to the electronic device 110 during the next contention-freeperiod in the next slot timestamp field 314. Consequently, eachelectronic device 110 can inspect these fields in a trigger frame 300 todetermine when the electronic device 110 can enter a low power mode.

For example, when a particular electronic device 110 is targeted by atrigger frame 300, such as by being listed first in the AID list field320, that electronic device 110 can determine a time corresponding tothe end of the transmission opportunity allocated to that electronicdevice 110 by inspecting the slot end timestamp field 312, relative tothe base timestamp field 310. The electronic device 110 can then enterthe low power mode when the current transmission opportunity expires. Inaddition, the electronic device 110 can determine a time correspondingto a next scheduled transmission opportunity allocated to the electronicdevice 110 by inspecting the next slot timestamp field 314, relative tothe base timestamp field 310. The electronic device 110 can then set awake-up timer corresponding to the start of the next transmissionopportunity allocated to the electronic device 110 during the nextcontention-free period. It will be appreciated that the scheduled accessmechanism allows the electronic device 110 to spend more time in the lowpower mode than the unscheduled access mechanism because the accesspoint 112 can indicate to the electronic device 110 during a currenttransmission opportunity when the next scheduled transmissionopportunity in the next contention-free period is scheduled to occur.Thus, all electronic devices 110 do not need to wake at the start of thenext contention-free period to listen for their trigger frame; instead,each electronic device 110 can wake at their expected transmissionopportunity as previously scheduled by the access point 112. Again, insome embodiments, the low power mode includes disabling the radio 114and/or signal processing circuitry associated with the physical layer ofthe WLAN.

FIG. 12 illustrates a diagram 1200 of a sleep cycle for a number ofelectronic devices utilizing the scheduled access mechanism tocommunicate via the WLAN, in accordance with some embodiments. Eachelectronic device 110 connected to the WLAN can wake up at the beginningof a corresponding transmission opportunity and listen to thecommunications medium to receive a trigger frame 300 targeted to thatelectronic device 110. It will be appreciated that, prior to the firstcontention-free period after the electronic device 110 connects to theWLAN, the electronic device 110 will be awake and is configured tolisten for a trigger frame 300 targeted at the electronic device 110.That trigger frame 300 includes information that specifies the nexttransmission opportunity for that electronic device 110, enabling theelectronic device 110 to enter the low power mode between transmissionopportunities.

As depicted in FIG. 12, at the beginning of the contention-free period1210, a first trigger frame 1012, transmitted by the access point 112,allocates a first transmission opportunity to a first electronic device110-1. The first electronic device 110-1 responds to the first triggerframe 1012 by transmitting a frame of station data 1022 to the accesspoint 112. The access point 112 then transmits an ACK frame 1032 to thefirst electronic device 110-1, ending the first transmissionopportunity. Once the first transmission opportunity is concluded, thefirst electronic device 110-1 can enter a low power mode, sometimesreferred to as a sleep mode. Prior to entering the low power mode, thefirst electronic device 110-1 can calculate a wake-up time, relative toa value of the TSF of the first electronic device 110-1, correspondingto the start of the next transmission opportunity allocated to the firstelectronic device 110-1. The first electronic device 110-1 can beconfigured to exit the low power mode at or prior to the wake-up time.In some embodiments, the electronic device 110 can set a wake-up timerbased on the time that corresponds to a start of a correspondingtransmission opportunity allocated to the electronic device during thesubsequent contention-free period as indicated by the next slottimestamp field 314 included in the trigger frame 300.

At some point between the end of the first transmission opportunity andprior to transmission of a second trigger frame 1014 during a secondtransmission opportunity, a second electronic device 110-2 wakes up andresumes listening to the communications medium. A second trigger frame1014, transmitted by the access point 112, allocates a secondtransmission opportunity to the second electronic device 110-2. Thesecond electronic device 110-2 responds to the second trigger frame 1014by transmitting a frame of station data 1024 to the access point 112.The access point 112 then transmits an ACK frame 1034 to the secondelectronic device 110-2, ending the second transmission opportunity.Once the second transmission opportunity is concluded, the secondelectronic device 110-1 can enter the low power mode. Prior to enteringthe low power mode, the second electronic device 110-2 can calculate awake-up time, relative to a value of the TSF of the second electronicdevice 110-2, corresponding to the start of the next transmissionopportunity allocated to the second electronic device 110-2. The secondelectronic device 110-2 can be configured to exit the low power mode ator prior to the wake-up time.

It will be appreciated that the first electronic device 110-1 and thesecond electronic device 110-2 are not configured to wake up at the sametime, like in the sleep cycle for the unscheduled access mechanism asillustrated in FIG. 9. Consequently, the ratio of an awake period to asleep period for each electronic device 110 can be reduced compared tothe sleep cycle for the unscheduled access mechanism, thereby savingmore power at the electronic device 110.

In some embodiments, the electronic device 110 can be configured toenter the low power mode immediately after the ACK frame is received bythe electronic device 110, even if there is still time remaining duringthe current transmission opportunity. In some embodiments, theelectronic device 110 can be configured to wake up prior to the start ofthe next allocated transmission opportunity to ensure that theelectronic device 110 does not miss the start of the next trigger frame300 targeted at the electronic device 110. For example, the wake-uptimer can be set to expire 50 microseconds ahead of the scheduled startof the next transmission opportunity.

In some embodiments, the slot end timestamp field 312 and the next slottimestamp field 314 include values relative to the beginning of thecontention-free period 1210. Thus, each electronic device 110 can onlyidentify a wake-up time for a particular transmission opportunity withinthe current contention-free period once the start time for thecontention-free period is identified. In such cases, all electronicdevices 110 are configured to wake up and listen to the communicationsmedium for a short time to identify the beginning of the contention-freeperiod, and then all but one electronic device 110 allocated the firsttransmission opportunity can enter the low power mode and wait until astart of a corresponding transmission opportunity within thecontention-free period. This type of operation can be important when thestart of the contention-free period can be delayed while contending foraccess to the communications medium with other WLANs.

FIG. 13 illustrates a diagram 1300 of access to the communicationsmedium by multiple WLANs, in accordance with some embodiments. Asdescribed above, at least some of the communications techniques canmonopolize the communications medium over legacy contention-based accessmechanisms where the delay between frames transmitted over thecommunications medium is too short for the contention-based accessalgorithms to acquire a transmission opportunity. This is an intentionalchoice by utilizing the SIFS (e.g., 16 microseconds) as the selecteddelay between frames and then immediately transmitting another frame,thereby not enabling, e.g., legacy Wi-Fi stations to reach a particularrandom back-off slot. However, where the communications medium is sharedamong multiple WLANs, some using the techniques described herein andothers using legacy communications protocols, care should be taken toensure shared access to the communications medium.

One technique for sharing access to the communications medium can beinherent simply based on the selection of the duration of thecontention-free period and the number of transmission opportunitiesallocated therein. For example, if long duration contention-free periodsare specified by the WLAN (e.g., 10 ms), and a small number ofelectronic devices 110 are connected to the WLAN (e.g., 4 devices), theneach electronic device 110 can be allocated a long duration for aparticular transmission opportunity (e.g., 2.5 ms). The natural effectof a long duration for each transmission opportunity is that theelectronic device 110 can finish transmission very early in thetransmission opportunity, allowing other WLAN stations in other WLANs toutilize the communications medium prior to the start of the nexttransmission opportunity within the contention-free period. For example,transmission of data between an electronic device 110 and the accesspoint 112 could be complete in 200 microseconds, leaving 2.3 ms in thetransmission opportunity to be utilized by other WLANs to transmit dataover the communications medium.

Another technique for sharing access to the communications medium can beimplemented by adjusting the duty cycle of contention-free periodsassociated with the WLAN to contention-based periods associated withother WLANs. As depicted in FIG. 13, the communications medium 1310 canbe divided into time slices 1320 at a particular frequency. Each timeslice 1320 can include a contention-free period 1330 that providesaccess to the communications medium 1310 for the WLAN. A duration of thecontention-free period 1330 is less than a duration of the time slice1320, enabling other WLANs to access the communications medium 1310outside of the contention-free period 1330.

By way of example as depicted in FIG. 13, the access point 112 can beconfigured to divide the communications medium 1310 into time slices1320 at a frequency of, e.g., 200 Hz. Each time slice 1320 is therefore5 ms in duration. Within each time slice 1320, the access point 112 canallocate resource units (e.g., transmission opportunities) to electronicdevices 110 connected to the WLAN within a contention-free period 1330having a duration of, e.g., 2 ms, leaving 3 ms of time in the time slice1320 for other WLANs to contend for access to the communications medium.Three time slices 1320-1, 1320-2, and 1320-3 are shown in FIG. 13 aswell as three corresponding contention-free periods 1330-1, 1330-2, and1330-3.

In some embodiments, the access point 112 utilizes contention-basedaccess mechanisms to get access to the communications medium 1310 fromother WLANs. For example, the access point 112 can implement carriersense techniques to determine when the communications medium 1310 isidle. The access point 112 can wait for the communications medium 1310to be idle for a specified delay (e.g., SIFS) before beginning thecontention-free period 1330. However, once the access point 112 hasacquired the communications medium 1310, the contention-free period 1330can allow unfettered access to the communications medium 1310 for theremainder of the contention-free period 1330 assuming transmissionscontinue unabated via the WLAN with minimal delays in between frames.

FIG. 14 presents a flow diagram 1400 illustrating an exemplary methodfor allocating transmission opportunities within a contention-freeperiod defined by an access point, in accordance with some embodiments.This method can be performed by one or more components included in anaccess point (and, more generally, an electronic device), such as aninterface circuit and/or a processing subsystem in access point 112 inFIG. 1.

At 1402, a contention-free period is defined by the access point. Insome embodiments, a processing subsystem included in the access pointimplements an algorithm to define a start time, an end time, and/or aduration of a contention-free period associated with a communicationsmedium utilized for communication between a set of electronic devicesconnected to a WLAN. In some embodiments, the communications mediumincludes one or more channels associated with a 5 GHz RF spectrum.

At 1404, a trigger frame is transmitted to the set of electronic devicesvia the communications medium. The trigger frame can be transmitted by,or in coordination with, an interface circuit included in the accesspoint. In some embodiments, the trigger frame can be transmitted fromthe access point to a multicast or broadcast address associated with theWLAN.

At 1406, a sequence of frames are received, via the communicationsmedium, from at least one of the electronic devices in the ordered listof electronic devices. The sequence of frames can be transmitted by, orin coordination with, the interface circuit included in the accesspoint. In some embodiments, the access point is configured to transmitacknowledgment frames to the electronic devices to acknowledgesuccessful receipt of one or more frames in the sequence of frames.

At 1408, at least two transmission opportunities are allocated withinthe contention-free period to electronic devices included in the orderedlist of electronic devices. In some embodiments, the processingsubsystem included in the access point is configured to implement analgorithm for determining which transmission opportunities are allocatedto corresponding electronic devices. The transmission opportunities canbe allocated according to an unscheduled access mechanism or,alternatively, according to a scheduled access mechanism.

FIG. 15 presents a flow diagram 1500 illustrating an exemplary methodfor reducing a power consumption associated with a wireless station, inaccordance with some embodiments. This method can be performed by one ormore components included in a station (and, more generally, anelectronic device), such as an interface circuit and/or a processingsubsystem in electronic device 110 in FIG. 1.

At 1502, an identifier positioned first in an ordered list of electronicdevices is read from a trigger frame. In some embodiments, theidentifier is an AID located in an AID list field of the trigger frame.

At 1504, the electronic device determines that the identifier isassociated with the electronic device. In some embodiments, a processingsubsystem compares the identifier to a stored identifier that uniquelyidentifies the device. In some embodiments, the identifier is an AIDthat is compatible with an 802.11 MAC address associated with theelectronic device.

At 1506, a frame is transmitted, via the communications medium, at atemporal position subsequent to an end of the trigger frame andassociated with the first communications medium being idle for a periodof time. In some embodiments, the electronic device is configured totransmit a data frame, via the interface circuit, over thecommunications medium after a delay period from the end of the triggerframe. The delay period can be set to a SIFS period of 16 microseconds.

At 1508, a wake-up timer is set based on a time associated with asubsequent contention-free period. In some embodiments, the electronicdevice is configured to exit a low power mode and listen to thecommunications medium at the expiration of the wake-up timer.

At 1510, a low power mode is entered subsequent to the transmission ofthe frame. In some embodiments, the low power mode can include disablingat least one of an antenna or an interface circuit communicativelycoupled to the antenna.

FIG. 16 presents a flow diagram 1600 illustrating an exemplary methodfor connecting to a WLAN, in accordance with some embodiments. Thismethod can be performed by one or more components included in a station(and, more generally, an electronic device), such as an interfacecircuit and/or a processing subsystem in electronic device 110 in FIG.1.

At 1602, an advertising packet is transmitted via a communicationsmedium associated with a WPAN. In some embodiments, the advertisingpacket is transmitted over a communications medium associated with aBluetooth Low Energy communications protocol. The communications mediumcan include one or more channels associated with a 2.4 GHz RF spectrum.

At 1604, a packet of information associated with a WLAN is received viathe communications medium associated with the WPAN. In some embodiments,the packet of information contains a BSSID as well as informationidentifying one or more channels associated with a separatecommunications medium utilized by the WLAN. The separate communicationsmedium utilized by the WLAN can include one or more channels associatedwith a 5 GHz RF spectrum.

At 1606, a trigger frame is received via the sepater communicationsmedium associated with the WLAN. The trigger frame can be received afterthe electronic device has connected to the WLAN by at least configuringthe interface circuit to listen to the one or more channels associatedwith the separate communications medium for any frames associated withthe BSSID included in the packet of information.

FIG. 17 presents a block diagram of an electronic device 1700 (which canbe an access point, another electronic device, such as a station or alegacy electronic device) in accordance with some embodiments. Thiselectronic device includes processing subsystem 1710, memory subsystem1712, and networking subsystem 1714. Processing subsystem 1710 includesone or more devices configured to perform computational operations. Forexample, processing subsystem 1710 can include one or moremicroprocessors, application-specific integrated circuits (ASICs),microcontrollers, programmable-logic devices, and/or one or more digitalsignal processors (DSPs).

Memory subsystem 1712 includes one or more devices for storing dataand/or instructions for processing subsystem 1710 and networkingsubsystem 1714. For example, memory subsystem 1712 can include dynamicrandom access memory (DRAM), static random access memory (SRAM), aread-only memory (ROM), flash memory, and/or other types of memory. Insome embodiments, instructions for processing subsystem 1710 in memorysubsystem 1712 include: one or more program modules or sets ofinstructions (such as program module 1722 or operating system 1724),which can be executed by processing subsystem 1710. For example, a ROMcan store programs, utilities or processes to be executed in anon-volatile manner, and DRAM can provide volatile data storage, and canstore instructions related to the operation of electronic device 1700.Note that the one or more computer programs can constitute acomputer-program mechanism, a computer-readable storage medium orsoftware. Moreover, instructions in the various modules in memorysubsystem 1712 can be implemented in: a high-level procedural language,an object-oriented programming language, and/or in an assembly ormachine language. Furthermore, the programming language can be compiledor interpreted, e.g., configurable or configured (which can be usedinterchangeably in this discussion), to be executed by processingsubsystem 1710. In some embodiments, the one or more computer programsare distributed over a network-coupled computer system so that the oneor more computer programs are stored and executed in a distributedmanner.

In addition, memory subsystem 1712 can include mechanisms forcontrolling access to the memory. In some embodiments, memory subsystem1712 includes a memory hierarchy that comprises one or more cachescoupled to a memory in electronic device 1700. In some of theseembodiments, one or more of the caches is located in processingsubsystem 1710.

In some embodiments, memory subsystem 1712 is coupled to one or morehigh-capacity mass-storage devices (not shown). For example, memorysubsystem 1712 can be coupled to a magnetic or optical drive, asolid-state drive, or another type of mass-storage device. In theseembodiments, memory subsystem 1712 can be used by electronic device 1700as fast-access storage for often-used data, while the mass-storagedevice is used to store less frequently used data.

Networking subsystem 1714 includes one or more devices configured tocouple to and communicate on a wired and/or wireless network (i.e., toperform network operations), including: control logic 1716, an interfacecircuit 1718 and a set of antennas 1720 (or antenna elements) in anadaptive array that can be selectively turned on and/or off by controllogic 1716 to create a variety of optional antenna patterns or ‘beampatterns.’ (While FIG. 17 includes set of antennas 1720, in someembodiments electronic device 1700 includes one or more nodes, such asnodes 1708, e.g., a pad, which can be coupled to set of antennas 1720.)For example, networking subsystem 1714 can include a Bluetoothnetworking system, a cellular networking system (e.g., a 3G/4G/5Gnetwork such as UMTS, LTE, etc.), a universal serial bus (USB)networking system, a networking system based on the standards describedin IEEE 802.11 (e.g., a WiFi® networking system), an Ethernet networkingsystem, and/or another networking system.

Networking subsystem 1714 includes processors, controllers,radios/antennas, sockets/plugs, and/or other devices used for couplingto, communicating on, and handling data and events for each supportednetworking system. Note that mechanisms used for coupling to,communicating on, and handling data and events on the network for eachnetwork system are sometimes collectively referred to as a ‘networkinterface’ for the network system. Moreover, in some embodiments a‘network’ or a ‘connection’ between the electronic devices does not yetexist. Therefore, electronic device 1700 can use the mechanisms innetworking subsystem 1714 for performing simple wireless communicationbetween the electronic devices, e.g., transmitting advertising or beaconframes and/or scanning for advertising frames transmitted by otherelectronic devices.

Within electronic device 1700, processing subsystem 1710, memorysubsystem 1712, and networking subsystem 1714 are coupled together usingbus 1728 that facilitates data transfer between these components. Bus1728 can include an electrical, optical, and/or electro-opticalconnection that the subsystems can use to communicate commands and dataamong one another. Although only one bus 1728 is shown for clarity,different embodiments can include a different number or configuration ofelectrical, optical, and/or electro-optical connections among thesubsystems.

In some embodiments, electronic device 1700 includes a display subsystem1726 for displaying information on a display, which can include adisplay driver and the display, such as a liquid-crystal display, amulti-touch touchscreen, etc. Display subsystem 1726 can be controlledby processing subsystem 1710 to display information to a user (e.g.,information relating to incoming, outgoing, or an active communicationsession).

Electronic device 1700 can also include a user-input subsystem 1730 thatallows a user of the electronic device 1700 to interact with electronicdevice 1700. For example, user-input subsystem 1730 can take a varietyof forms, such as: a button, keypad, dial, touch screen, audio inputinterface, visual/image capture input interface, input in the form ofsensor data, etc.

Electronic device 1700 can be (or can be included in) any electronicdevice with at least one network interface. For example, electronicdevice 1700 can include: a cellular telephone or a smartphone, a tabletcomputer, a laptop computer, a notebook computer, a personal or desktopcomputer, a netbook computer, a media player device, an electronic bookdevice, a MiFi® device, a smartwatch, a wearable computing device, aportable computing device, a consumer-electronic device, an accesspoint, a router, a switch, communication equipment, test equipment, aswell as any other type of electronic computing device having wirelesscommunication capability that can include communication via one or morewireless communication protocols.

Although specific components are used to describe electronic device1700, in alternative embodiments, different components and/or subsystemscan be present in electronic device 1700. For example, electronic device1700 can include one or more additional processing subsystems, memorysubsystems, networking subsystems, and/or display subsystems.Additionally, one or more of the subsystems can be omitted in electronicdevice 1700. Moreover, in some embodiments, electronic device 1700 caninclude one or more additional subsystems that are not shown in FIG. 17.Also, although separate subsystems are shown in FIG. 17, in someembodiments some or all of a given subsystem or component can beintegrated into one or more of the other subsystems or component(s) inelectronic device 1700. For example, in some embodiments program module1722 is included in operating system 1724 and/or control logic 1716 isincluded in interface circuit 1718.

Moreover, the circuits and components in electronic device 1700 can beimplemented using any combination of analog and/or digital circuitry,including: bipolar, PMOS and/or NMOS gates or transistors. Furthermore,signals in these embodiments can include digital signals that haveapproximately discrete values and/or analog signals that have continuousvalues. Additionally, components and circuits can be single-ended ordifferential, and power supplies can be unipolar or bipolar.

An integrated circuit (which is sometimes referred to as a‘communication circuit’) can implement some or all of the functionalityof networking subsystem 1714. This integrated circuit can includehardware and/or software mechanisms that are used for transmittingwireless signals from electronic device 1700 and receiving signals atelectronic device 1700 from other electronic devices. Aside from themechanisms herein described, radios are generally known in the art andhence are not described in detail. In general, networking subsystem 1714and/or the integrated circuit can include any number of radios. Notethat the radios in multiple-radio embodiments function in a similar wayto the described single-radio embodiments.

In some embodiments, networking subsystem 1714 and/or the integratedcircuit include a configuration mechanism (such as one or more hardwareand/or software mechanisms) that configures the radio(s) to transmitand/or receive on a given communication channel (e.g., a given carrierfrequency). For example, in some embodiments, the configurationmechanism can be used to switch the radio from monitoring and/ortransmitting on a given communication channel to monitoring and/ortransmitting on a different communication channel. (Note that‘monitoring’ as used herein comprises receiving signals from otherelectronic devices and possibly performing one or more processingoperations on the received signals)

In some embodiments, an output of a process for designing the integratedcircuit, or a portion of the integrated circuit, which includes one ormore of the circuits described herein can be a computer-readable mediumsuch as, for example, a magnetic tape or an optical or magnetic disk.The computer-readable medium can be encoded with data structures orother information describing circuitry that can be physicallyinstantiated as the integrated circuit or the portion of the integratedcircuit. Although various formats can be used for such encoding, thesedata structures are commonly written in: Caltech Intermediate Format(CIF), Calma GDS II Stream Format (GDSII) or Electronic DesignInterchange Format (EDIF). Those of skill in the art of integratedcircuit design can develop such data structures from schematic diagramsof the type detailed above and the corresponding descriptions and encodethe data structures on the computer-readable medium. Those of skill inthe art of integrated circuit fabrication can use such encoded data tofabricate integrated circuits that include one or more of the circuitsdescribed herein.

While the preceding discussion used a Wi-Fi communication protocol as anillustrative example, in other embodiments a wide variety ofcommunication protocols and, more generally, wireless communicationtechniques can be used. Thus, the communication technique can be used ina variety of network interfaces. Furthermore, while some of theoperations in the preceding embodiments were implemented in hardware orsoftware, in general the operations in the preceding embodiments can beimplemented in a wide variety of configurations and architectures.Therefore, some or all of the operations in the preceding embodimentscan be performed in hardware, in software or both. For example, at leastsome of the operations in the communication technique can be implementedusing program module 1722, operating system 1724 (such as a driver forinterface circuit 1718) or in firmware in interface circuit 1718.Alternatively, or additionally, at least some of the operations in thecommunication technique can be implemented in a physical layer, such ashardware in interface circuit 1718. In some embodiments, thecommunication technique is implemented, at least in part, in a MAC layerand/or in a physical layer in interface circuit 1718.

Furthermore, in general, the communication technique can be used tofacilitate scheduled channel access in time and/or frequency inconjunction with multi-user multiple input multiple output (MU-MIMO)and/or OFDMA.

It is well understood that the use of personally identifiableinformation should follow privacy policies and practices that aregenerally recognized as meeting or exceeding industry or governmentalrequirements for maintaining the privacy of users. In particular,personally identifiable information data should be managed and handledso as to minimize risks of unintentional or unauthorized access or use,and the nature of authorized use should be clearly indicated to users.

The various aspects, embodiments, implementations or features of thedescribed embodiments can be used separately or in any combination.Various aspects of the described embodiments can be implemented bysoftware, hardware or a combination of hardware and software. Thedescribed embodiments can also be embodied as computer readable code ona computer readable medium for controlling manufacturing operations oras computer readable code on a computer readable medium for controllinga manufacturing line. The computer readable medium is any data storagedevice that can store data which can thereafter be read by a computersystem. Examples of the computer readable medium include read-onlymemory, random-access memory, CD-ROMs, HDDs, DVDs, magnetic tape, andoptical data storage devices. The computer readable medium can also bedistributed over network-coupled computer systems so that the computerreadable code is stored and executed in a distributed fashion.

The foregoing description, for purposes of explanation, used specificnomenclature to provide a thorough understanding of the describedembodiments. However, it will be apparent to one skilled in the art thatthe specific details are not required in order to practice the describedembodiments. Thus, the foregoing descriptions of specific embodimentsare presented for purposes of illustration and description. They are notintended to be exhaustive or to limit the described embodiments to theprecise forms disclosed. It will be apparent to one of ordinary skill inthe art that many modifications and variations are possible in view ofthe above teachings.

What is claimed is:
 1. An access point, comprising: one or more nodesconfigured to communicatively couple to an antenna; an interfacecircuit, communicatively coupled to the one or more nodes, configured tocommunicate with a set of electronic devices in a wireless local areanetwork (WLAN), and configured to cause the access point to: transmit,via a communications medium associated with the WLAN, a trigger frame tothe set of electronic devices, the trigger frame including informationspecifying an ordered list of electronic devices in the set ofelectronic devices that are allowed to transmit data within the WLAN viathe communications medium, each electronic device triggered to transmitrespective data sequentially and non-overlapping in time with data fromother electronic devices based on the ordered list of electronicdevices, and receive a sequence of frames from at least two electronicdevices in the ordered list of electronic devices via the communicationsmedium during a contention-free period, each frame including a qualityof service (QoS) control field indicating a QoS type and a priorityvalue for data included in the frame; and a processing subsystem,communicatively coupled to the interface circuit, and configured tocause the access point to: define the contention-free period associatedwith the communications medium; and allocate at least two transmissionopportunities within the contention-free period to the at least twoelectronic devices in the ordered list of electronic devices, whereinallocation of transmission opportunities to each of the at least twoelectronic devices is based at least in part on QoS types and priorityvalues received from the at least two electronic devices in one or moreprevious contention-free periods.
 2. The access point of claim 1,wherein a start of each transmission opportunity in the at least twotransmission opportunities within the contention-free period is adjusteddynamically by the processing subsystem based on traffic transmitted viathe communications medium.
 3. The access point of claim 2, wherein atransmission opportunity is terminated in accordance with transmissionof an acknowledgment frame that indicates the access point received atleast one frame from a corresponding electronic device.
 4. The accesspoint of claim 2, wherein: each transmission opportunity is associatedwith a maximum duration, and a duration of a particular transmissionopportunity can be less than or equal to the maximum duration.
 5. Theaccess point of claim 1, wherein each electronic device is configured toenter a low power mode at an end of a corresponding transmissionopportunity allocated to the electronic device and wake up to listen tothe communications medium prior to a start of a next contention-freeperiod.
 6. The access point of claim 5, wherein a time associated withthe start of the next contention-free period is indicated within thetrigger frame.
 7. The access point of claim 1, wherein a start of eachtransmission opportunity in the at least two transmission opportunitieswithin the contention-free period is fixed by the processing subsystemaccording to a schedule based at least in part on the QoS types andpriority values previously received from the at least two electronicdevices.
 8. The access point of claim 7, wherein a duration of eachtransmission opportunity within the contention-free period is equal to aduration of the contention-free period divided by a number of electronicdevices in the ordered list of electronic devices.
 9. The access pointof claim 7, wherein each electronic device is configured to enter a lowpower mode at an end of a corresponding transmission opportunityallocated to the electronic device and wake up to listen to thecommunications medium prior to a start of a corresponding transmissionopportunity allocated to the electronic device during a nextcontention-free period that is subsequent to a start of the nextcontention-free period.
 10. The access point of claim 1, wherein theprocessing subsystem is configured to cause the interface circuit tore-transmit the trigger frame to a corresponding electronic deviceappearing first in the ordered list of electronic devices when theaccess point fails to receive a frame of data from the correspondingelectronic device within a threshold time of an end of transmission ofthe trigger frame.
 11. An electronic device, comprising: one or morenodes configured to communicatively couple to an antenna; and aninterface circuit, communicatively coupled to the one or more nodes,configured to communicate with an access point in a wireless local areanetwork (WLAN), and configured to cause the electronic device to:receive, from the access point, a trigger frame that includesinformation specifying an ordered list of electronic devices in a set ofelectronic devices that are allowed to transmit data via a firstcommunications medium during a contention-free period, each electronicdevice in the set of electronic devices triggered to transmit respectivedata sequentially and non-overlapping in time with data from otherelectronic devices based on the ordered list of electronic devices, andtransmit a frame at a temporal position in a sequence of frames based onthe ordered list of electronic devices during the contention-freeperiod, the frame including a quality of service (QoS) control fieldindicating a QoS type and a priority value for data included in theframe; and a processing subsystem, communicatively coupled to theinterface circuit, and configured to cause the electronic device to:read an identifier positioned first in the ordered list of electronicdevices from the trigger frame, determine that the identifier isassociated with the electronic device, transmit the frame at thetemporal position subsequent to an end of the trigger frame andassociated with the first communications medium being idle for a periodof time, identify a time associated with a subsequent contention-freeperiod, and enter a low power mode subsequent to transmission of theframe, wherein the access point allocates transmission opportunities tothe electronic devices in the set of electronic devices based at leastin part on QoS types and priority values received from the set ofelectronic devices in one or more previous contention-free periods. 12.The electronic device of claim 11, wherein the interface circuit isconfigured to cause the electronic device to: transmit an advertisingpacket to the access point via a second communications medium associatedwith a wireless personal area network (WPAN); receive, via the secondcommunications medium, a packet of information associated with the WLAN,wherein the information includes a basic service set identifier (BSSID)for the WLAN, and receive, via the first communications mediumassociated with the WLAN, the trigger frame.
 13. The electronic deviceof claim 12, wherein: the first communications medium comprises one ormore channels within a 5 GHz radio frequency (RF) spectrum, and thesecond communications medium comprises one or more channels within a 2.4GHz RF spectrum.
 14. The electronic device of claim 11, wherein theperiod of time is approximately 16 microseconds.
 15. The electronicdevice of claim 11, wherein a wake-up timer is set based on a time thatcorresponds to a start of the subsequent contention-free period.
 16. Theelectronic device of claim 11, wherein a wake-up timer is set based on atime that corresponds to a start of a corresponding transmissionopportunity allocated to the electronic device during the subsequentcontention-free period as indicated by a timestamp included in thetrigger frame.
 17. A method for transmitting a frame from an electronicdevice configured to communicate with an access point in a wirelesslocal area network (WLAN), the method comprising: by the electronicdevice: reading an identifier positioned first in an ordered list ofelectronic devices included in a trigger frame received, via aninterface circuit of the electronic device, from the access point duringa contention-free period, determining that the identifier is associatedwith the electronic device, transmitting, during the contention-freeperiod subsequent to an end of the trigger frame and after a period oftime during which a first communications medium associated with the WLANis idle, a frame to the access point in response to receiving thetrigger frame, the frame including a quality of service (QoS) controlfield indicating a QoS type and a priority value for data included inthe frame, receiving an acknowledgment frame from the access point,identifying a time associated with a subsequent contention-free periodas specified within the trigger frame, and entering a low power modesubsequent to transmission of the frame, wherein: each electronic devicein the ordered list of electronic devices triggered to transmitrespective data sequentially and non-overlapping in time with data fromother electronic devices based on the ordered list of electronicdevices, and the access point allocates transmission opportunities tothe electronic devices in the ordered list of electronic devices basedat least in part on QoS types and priority values received from the setof electronic devices in one or more previous contention-free periods.18. The method of claim 17, the method further comprising: by theelectronic device: transmitting an advertising packet to the accesspoint via a second communications medium associated with a wirelesspersonal area network (WPAN); receiving, via the first communicationsmedium, a packet of information associated with the WLAN, wherein theinformation includes a basic service set identifier (BSSID) for theWLAN, and receiving, via the first communications medium associated withthe WLAN, the trigger frame.
 19. The method of claim 18, wherein theWPAN is associated with a Bluetooth Low Energy communications protocol.20. The method of claim 17, wherein a wake-up timer is set based on atime that corresponds with a start time of a transmission opportunityallocated to the electronic device during the subsequent contention-freeperiod, the start time of the transmission opportunity indicated by atimestamp included in a field of the trigger frame.